I use Nova and I haven't had any issues using it with the beta. One thing I noticed though and tested with other launchers is that when leaving the recent screen just pops out of existence instead of a showing an animation.
You are welcome to use any third party app you wish during beta program. As we don't have access to source of the app, we wont be able to support any error reports regarding app. 3rd party app errors need to be handled by corresponding app developers.
