All the new features and compatibility with new programs. In the case of NT5 (2K/XP to NT6 (Vista/7/8) there's an extremely large number of changes for the good, including full-screen hardware acceleration, updating multiple APIs, new driver models, and more. There's modern programs that
require Vista/7 to run because the technologies they use did not exist in XP and below, in fact.
The Windows Volume Mixer works off the new sound drivers and now allows programs to record the entire computer and/or mute certain programs instead of having
just a single volume level for the whole machine. Recording programs that work off of those features need them to exist. This is something that makes game recording in Vista/7/8 much better as a single program can do something like record your game's sound, Skype's sound, and your microphone at once. Otherwise you'd need to record all three separately at the same time and then mix them later.
First, no. As far as instability, some of the changes to the driver model in Vista/7/8 make it so that when something like your sound or video driver crashes, it no longer causes the BSoD and shuts down the whole computer. Instead Windows unloads that driver (halting it's execution) and reloads it. So this is one example of the newer OS being
more stable, because a bug in a third-party driver won't break
everything else when it decides to go bad.
Second, yes (obviously new stuff is different), but people have to get over their innate human fear of !!!DIFFERENT!!! at some point in their life, and hopefully it happens well before they go off and take part in a business. A business that refuses to upgrade something merely because the new thing is different... that's stagnation.
Step 1 - Fire it up.
Step 2 - Use it.
Step 3 - Does it work? Y/N
As a less-snarky response, if a program does not even have compatibility with NT6, either that's an old version you need to update, or if there are no updates then there is likely no support either, which is a big issue in a business, and a sign that an alternative may be needed.
For example the older version of Deep Freeze in use by my college on their XP machines (which had been set up some years ago) had some small bugs with 7. So what did we do? We downloaded the latest version from Faronics, stuck a copy on the servers, and started using that version on all the machines. Problem solved (and it even took one less click to do a commonly-done task).
The question should not be "is my business suitable to use this program?" The question is "does this program work for my business"? If the answer is no, look into alternative products. Software is a business as well, and there are competitors out there. In almost every case there's a number of different companies that make programs aimed to solve the same problems. Hell, even for more technical tasks like OS virtualization there's VMWare, Virtualbox, MSVPC, and more.
If the employees only had the most basic of computer know-how, then I could see this being an issue...
But that's a problem with your employees. If one of your employees is unable to do his job anymore because you painted a machine a different color or replaced a sign on a door with one that has a different font and a colored background, you might want to re-consider who you're hiring. Perhaps only hire highschool graduates, GED holders, and other people who can show they have learned basic modern skills, such as problem-solving and pattern-recognition that everybody is expected to have once they reach workable age.
I'm being demeaning towards them because the differences are not nearly large enough to confound anybody who... you know,
knows how to use a modern computer. There's still three buttons in the upper-right of programs, they're still in the same order and still have the same function. The task bar is at the bottom and has the start menu on the left, and notification icons on the right with programs in the middle. The desktop still has icons. Browsers still have their task bars at the top of the page. So on and so forth.
http://en.wikipedia.org/wiki/MS-DOS_Editor
Ever used that program? It's a text editor.
"Why would somebody ever upgrade to something newer? As that program shows, you don't need a whole 64MB of RAM for a text editor!"