Is the Firefox 6 Beta stable?

By definition, Beta releases are never stable. The only truly stable releases are usually called just “stable” or “final”.

If you’re curious, definitely try it out. But keep the old version if something goes wrong.

That depends on your idea of “stable”.
By definition, a Beta version of software is intended for user testing, not for release. It is less stable than the release version. It’s intended that it will break and that you, the user, will file bug reports to Bugzilla so that the developers will know what to fix.
A Beta is still more stable than an Alpha, which is newer code that has barely been tested at all.

Long story short: you can probably try out the beta without hurting anything- but keep your old version of Firefox in case something blows up.

Well guys, I tried it out but some of my most important add-ons aren’t yet compatible so it has promptly been uninstalled.
Thanks anyway.