Compared to other carts, it's got a simple and basic menu system. That's great for some people who value simplicity (it's extremely easy to use). Other people want more features. If you want more features, I'd recommend the Acekard 2 which is only a few dollars more at dealextreme.
The most annoying thing about the DSTT is that its menu doesn't sort roms alphabetically. It also doesn't let you categorize your roms into folders (they are all shown in a single list in the menu), and you need to use a loader program like GBA ExpLoader to run the Opera browser or GBA games (more info on that below). There is a homebrew menu system for the DSTT called YSMenu that overcomes some of the shortcomings of the official menu system (it sorts roms, it displays folders, and it can run GBA games and browser without a loader program if you have a slot2 GBA expansion cart).
Setting it up is easy:[*]Download the firmware. You can get it here:
http://gbatemp.net/index.php?download=2134[*]Unzip the firmware archive. It should have a file named TTMENU.DAT and a folder named TTMENU (which will contain a bunch of files). Drag TTMENU.DAT and the TTMENU folder onto your microSD card.[*]Make a new folder on your microSD card called "games."[*]Put one or two .nds files into the "games" folder.[*]Remove the microSD card from your PC. Make sure you always use the "safely remove hardware" to remove the microSD card.[*]Insert your DSTT into your NDS. Insert the microSD into your DSTT. You should get to a menu with your games in it. Click on a game to run it.Yes, you can usually connect your NDS with a WiFi router, but some are easier to set up than others. Whether or not you'll be able to use WiFi has nothing to do with which flash cart you use -- they all work with WiFi if you're able to connect to WiFi with your NDS.
There are homebrew browsers that work without slot2 memory, but none of them support images very well. If you want to use the Opera browser, you have to have a slot2 GBA expansion cart. These carts also have the advantage that they let you play GBA games that are stored on your DSTT. The eWin 2in1 GBA expansion cart is relatively cheap (~$14 shipped at psxboy.com). The DSTT will also work with the EZ 3in1. You'll need to grab the latest version of GBA ExpLoader to make the slot2 cart work with the browser or with GBA games, available here:
http://kotei.blog.so-net.ne.jp/archive/c530-1
Yes, the DSTT works with most homebrew, but as with all flash carts some homebrew isn't compatible with all carts.
-Bri