It all depends on how you use your trem and what your priorities are.
If you like the really loose, fluid feel of the Edge and you like to do whammy tricks like flutters, the TremSetter isn't for you.
I've got one installed on one of my guitars and i quite like it for the following reasons:
1. It has a nice, stiff feel
2. If you break a string, the bridge stays put and doesn't go out of tune (provided you've got the TremSetter tension really cranked up)
3. It returns to pitch extremely well (again, with it cranked up) but it's got a bit of a "detent" feel in its centre position, which can make subtle trem use difficult
4. High frequencies don't seem to be bled off as much by the trem, giving you a bit more "shimmer" in your sound, akin to having a fixed or blocked trem... and you can still pull up on the trem
You can loosen the TremSetter to get a smoother feel (which is what i do), but you lose benefit #2.
For me, it's worth it for the tonal benefits to lose the ability to flutter.