Touch wood, I'm not either. I also hesitated before taking the step from Vegas 6 but now have no regrets but I suppose much will depend on the sort of work you are doing and the specs of your PC.
Install it, open some of your recent projects, save them with "-V8" suffixes and see if they work for you. If it prangs, no harm done, you've still got whatever version you had installed before still available so you're no worse off. Even if no one said they're having a problem you'd be nuts to not test any new release before committing serious hours to it.
8.0b seems to work for most people on this forum. I am running it using Vista, and on most projects it seems to work flawlessly, however there are times where it appears to choke when you fill up the timeline with losts of jpegs etc. and I seem to be getting memory management problems. I think the success of running vegas is proprtional to the media and amount of media used within it.
I agree with Bob, and I suggest just give it a test run on some of your more demanding projects. Be sure to rename them after loading them, so you do not overwrite the previous version Veg.