It's still not v1 where there would be some sort of backward compatibility guarantee, but it's close if you are using master. Note though that even without that guarantee, there is git-bug-migration to provide you some safety.
There is however some bugs and missing features, as in any software that young with an author busy buying/refurbishing an apartment ;)
> This is now more than a proof of concept, but still not fully stable. Expect dragons and unfinished business