Ok, this thread needs some basic CS knowledge.
First off, you keep ranting about SSDs, and how fast/slow they are. Now, not having one makes my argument kinda moot, but i know what technology theyre based on. The facts are this:
Its fast reading, but not really writing. This doesnt really matter to vista though - by some bizzare chance theyve done the caching system right, and it pre-warms the most used program on a semi-intelligent algorithm, so the programs launched the most (IE, Firefox for example) will be put there. I bet its flushed from time to time, so once in a while youll feel theres a bit slowdown there. However, except for either really large programs, or the ones you constantly close-open (again, IE, Firefox) you will not feel a difference in speed, maybe responsiveness, but not speed. The technology for this is in fact nothing new, and has beed introduced in OSX 10.2 Jaguar if memory serves right, except its not caching to a disk, but RAM - and this is fine, because as somebody said, it doesnt take a lot of time to free memory, but it takes a lot of time (well, CPU-cycles wise) to load a program from a hard disk. If the memory is not used anyway, why clear it? Its just waste of space. This is of course given you have a smart-enough algorithm to judge what would be good to leave in memory, and what not. OSX does this right, i dont know about vista - never done any benchmark. Too bad Linux doesnt have this at all
I think windows doesnt say it, but under OSX, it doesnt show you free/used memory. You have Active memory - the amount that is actively beeing used, and Inactive - meaning something was there and wasnt deleted, because it may come in handy in a while. However, if an app requests more memory, and there is no free memory left, OSX will assign inactive memory (cleaning it as needed first). And this is the _best_ way to be done.
Another thing - Vista security. It has none. Folks, trust me when i say this - the pitifull sandboxing of IE and UAC is a poor implementation of what Unix done ages ago - which is tight user priviledge control. One problem is on the system backend - the whole need of a OS to have a firewall and anti-virus software to guard SYSTEM services automatically disqualifies it as a secure OS. A good written service/daemon will NOT accept malformed data (which is what windows frequently does), nor will it accept input from unauthorized sources (for example, i can never imagine my window server (X) beeing brought down because someone sent a magic packet over the network - its by default configured to NOT accept data from anywhere else than the process that ran it - not even from a different user on the same machine). Even more, the user and his application should have NO right to even remotely touch both system files and interfaces except the ones that have been programmed especially for it. The only exception is when the user elevates his rights, for a certain time period. This is not how it was done in XP - every process ran as user (who had admin rights) and could pwn the system. Of course, under XP you could take away admin right, but most apps borked out at this setting, because they assumed no one is going to do this. Vista supposedly now mandates this mechanism - but do not be fooled. Instead of fixing the problem at its core - clear seperation of Userspace and OS-Space, its a bandaid that says "ok, from now on this needs to be run from a specific app (UAC process) and the rest is as it was". Because of this UAC kicks in WAY to often (for simple stupid things like changing the screen resolution, or chaning from DHCP to static ip addresses). Because of this the UAC is only a buton - which soon people are going to click "Accept" as soon as they see it. So much for user-concious security. If UAC was done right from a UI standpoint it would display the full path of the app, and prompt the user to intput his password. Think how obnoxious THAT would be.
Last thing - speed. It's slower, the reason for it - this is Microsofts first attempt to seperate Kernel mode drivers from user-space interfaces. Theres no secret that overtime the NT kernel which is supposedly microkernel has grown to be a macrokernel. This is not a good thing, because switching from userspace to kernel space takes a long time for the processor, and theres a lot of overhead in this (this is what bugged the early Mac OS X - but as caches and processors got faster the problem fixed itself. Also the Darwin guys really gave it their best).
The other thing is that Microsoft is shooting itself in the foot in backwards compatibility. As it is now there are 3 APIs in Vista to program for WinNT, Win32, .Net. And lets not forget that not so long ago in XP the Windows 3.11 API was still there! Because Vista has to take care of all the quirks and hacks that each of these APIs has, the system stability goes down, as well as speed. What MS should have done is to delegate the old APIs to some kind of virtualization (think Wine, or Mac Classic) and let only one API roam free (.Net). All can see that Microsoft is betting on managed code - a noble goal, which will take away their inability to make sure that code is safe to run (and i mean from buffer overflows, or stack overruns for example - not safe in a virus way). We'll see how that goes in the next Windows (7?)
Theres the 64bit debate. Its not emulation people. In fact, your 64bit processors arent exactly 64 bit per se. A quick guide then. A 32bit x86 processor had bunch of instruction, 32bit long word, and 8 regiters (little spaces of memory about 4kb each, very close to the processors). Your 64bit processor differs that it has 16 registers, and has about a dozen (someone correct me on the specific amount please) of 64bit word long instructions. All 32bit instructions are just prefixed with zeroes. It doesnt really matter - since the Pentium, all of x86 instructins are actually broken down into tiny MIPS micro-ops, and executed as the architecture designers saw fit (this is all what the decode stage in the processor is all about). Think of x86 and x64 as a really-low programming language, not an end. However, about windows. What happens when you run a 32bit program in a 64bit windows enviroment is WOW32 is started, and it only redirects the programs DLL requests to 32bit versions of those DLLs. For example, lets say were runnign winamp. If winamp is 64bit, it would ask for dsound.dll and would get it from /Windows/System64/dsound.dll. This would result in it loading 64bit code for direct sound. However, if winamp is 32bit, loading a 64bit dll won't work at all - this is when WOW32 comes it - when winamp asks for dsound.dll wow32 redirects the request from the usual directory to the 32bit one, lets say /Windows/System32/dsound.dll. This loads the 32bit version of the direct sound dll and all is good. Also, it *translates* some specific 32bit calls to 64bit ones (mainly the register and stack initialization procedures) and notifies the CPU that this is a 32bit process.
Lastly - DirectX 10. I program in OpenGL, but ill say this - something is rotten in DirectX 10 nation. For real, the thing is SO slow (check any benchmark of any game that supports both X9 and X10), and the compatibility of DX9 has gone the way of the do-do. While Psychonauts (a DX8.1 game which runs on a Xbox1!) runs perfectly on my GMA950 equipped Macbook, in Vista when a little bit over 3000k vertices come up, it crawls to a halt. I check on my GeForce 6600GT and the result was EXACTLY the same - they were both _equally_ slow under Vista! And looking at the tech specs DirectX10 was supposed to speed up everything (thru virtualizing both shaders and video memory space), not slow it down to a crawl! I have no idea how theyre gonna get out of this one - no company is willing to risk going DirectX10 only, except Microsoft itself. They cant even seek refuge in Xbox360, because the chip there is DX9 and so is the (stable now) API.
Uff, that was a long write, im almost done here folks ;] To recoup the question - could Vista be an update to XP? Definitely NO. Too much (mainly good things) happened under the hood. Too bad none of the userspace programs show the new functionality. For this, i would bet we need to wait for Vista+1. Good night everyone