In a PSA environment, no its not stable.
It really depends on the package. The general rules are maintenance releases go into [atomic-testing] for testing. If all goes well, that will be published into [atomic].
Anything I feel like will break something, or that I have no experience with, will go into [atomic-bleeding]. I don't consider anything in atomic-bleeding the kind of thing I consider release-worthy at this time. For example, php and mysql in that channel are back ports from FC5 and FC6. There are known integration issues with PSA on both. They're stable in that they wont crash, and that they'll work fine (most likely) in a non-PSA environment. They're unstable in that PSA will not work with them 100%.