My experiences so far have been positive. The machine I installed it upon (see above) has been rock solid, without any driver issues. Haven't used it enough to notice any performance boost, but it is up 24/7 and I check in occasionally to do some surfing & whatnot.
If there ARE problems, the concensus seems to be you'll notice right away: video problems, hung installation, drivers disappearing from the hardware wizard. In my case, the eFax client stopped working but was fixed easily by reinstalling it. So if you're confident your backup images are current, I'd say it's safe enough to try.
But I'd wait until after any mission-critical deadlines are past. If things go awry, restoring a disk image from backup can eat up a lot of time. :-)