I have been enjoying SimplyMEPIS 7.0 since Beta 1. Have updated it several times. I did also install Beta 5, but generally just updated every so often. My recollection of exactly what else I did is spotty, but I MAY have either downloaded one of the release candidates or simply upgraded again.
When the final came out, I definitely just upgraded from the earlier test releases. All that really changed in the end was the physical appearance of the default setup.
The SimplyMEPIS test code was so solid that quite frankly, even the test releases exceeded the stability of most released projects. The final release is even more so. I have not detected any issues at all so far.
I recommend two distros for desktop use, both Debian based. The first is SimplyMEPIS for every day, stable desktop use. You can't get a more solid desktop, and it is simple, plus it comes with plenty of software, with the capability of adding additional stuff if something you like is missing in the distribution itself. The other one is sidux 2007.04. The sidux software is a variation of Debian unstable. Essentially the sidux project takes Debian unstable, adds their own repositories to correct problems in Debian Sid, then adds their own appearance and some very good administrative tools. They also beef up hardware support and accelerate bug fixes. It is a rolling upgrade release. For bleeding edge, yet surprisingly usable, generally stable software, sidux is the best.
Conservative, want stability first plus simplicity? SimplyMEPIS is first rate.
An experimenter, willing to take a chance? Like the latest and greatest? Then sidux is for you!