I've been quite impressed with CM7. I downloaded the most recent RC and everything works. I did have to do the GPS fix, but I'm used to that, having needed it for MIUI as well.
Ok, for you non-software developers:
nightly builds incorporate any work done during that day and got checked in to the main code line. Typically the developer will run a local build on his/her local machine to make sure their code doesn't cause the build to fail. But just because a dev doesn't break the build doesn't mean they didn't introduce bugs with their code. Therefore, bugs can appear and go away with any nightly build.
A "RC" is a "release candidate." This particular build has undergone some degree of QA (quality assurance [testing]). Bugs were caught and fixed. Major functionality is working. Could be minor bugs that still need to be addressed before it is "production ready."
"Production ready" builds are called all sorts of things. Commonly, you see it as a "stable" build. It can also be referred to as "GA (general acceptance)" or "Production" build. These typically undergo standard QA where bugs are found and fixed, and then the build has undergone "UAT (user-acceptance testing)." This is commonly a "beta" release where a subset of non-developers test the version and report any bugs they find. These bugs are then addressed. New functionality is not added. Expect little to no bugs for stable releases.