This is inaccurate. Raid56 have always been labeled experimental, but recently, data corruption bugs were found which make it dangerous to use.

Other raid levels (raid0, raid1, raid10) work fine and are considered stable -- at least as stable as the filesystem itself.

Either way, if you care about the data, you must backup, no matter what fs you use.

Apologies, I only saw the recent mailing list post which basically said "we're removing the ability to even compile support for raid56". I didn't mean to say that btrfs was overly-zealous in their trust of new code (I personally am super excited for the future of btrfs).