You don't think function of things like the camera or gps or audio recorder known not to work in some roms have to do with whether we should root? I disagree. One poster mentioned that all roms have flaws. How in the world can a person make a rational decision about whether to root if we know what we may gain but NOT what we may lose?
I'd put the relevance of the ROM question in relation to the OP in a gray area, but since you ask, here's the deal...
At this moment, there has been no "official" Gingerbread offerings for the Thunderbolt. There was a leak several weeks ago (that definitely was not ready for prime time), and a few builds that have been ported over, but no real base image to work off of, and as of yet, no source for the kernel (which is important). This is why, in my opinion, the Gingerbread ROMs are really not as stable as the Froyo ones.
A lot of folks will comment that certain GB Roms are great, and while I'm not saying that they're wrong, I have yet to find one that doesn't have bugs.
If you really want a stable, bug free ROM, then I suggest going Froyo. I'm running BAMF Remix 1.8.6 as my everyday ROM, and it's really nice. Everything works, no problems whatsover, plus a lot of great features and customizations you can't get with the stock OS.
In other words, if you want "stable", go Froyo...if you want to play around with some of the latest Android and HTC Sense features and don't mind having to deal with or fix a few bugs along the way, then by all means, give GB a run. The great thing is, once you're rooted, you can always go back if you install something you don't like.