Be aware that there may be larger bugs hiding in these
I can guarantee that there are plenty of bugs when running HEAD on their master. I have yet to have something cause me to loose work though, but it's only a matter of time I guess.
Remember. If you encounter bugs in the nightlies, report them on the bugtracker.
a59d1, I assume you mean the nightlies released under the 6.0.0RC name, Be aware that there may be larger bugs hiding in these, as they are development builds, the 6.0.0 is just a name they decided on, realistically its 5.0.1 or 5.1.0 alpha.
I'm aware, but reporting a minor bug here and there (with fixes within 24 hours, usually) make it worth it. I'm happy to contribute to the project.