As a result of the discussions, I'm now reconsidering using Mouse in TB2. Its interesting, it's not for any of the reasons I thought, but for a distressing encapsulation breech built into Moose.
The main concern is that the fact that we're using Mouse leaks out. We must document that we're using Mouse and users must rely on this implementation detail. Anything wishing to consume a role must use Mouse. Anything wishing to take full advantage of subclassing must use Mouse. This is a critical violation of encapsulation. It means TB2 is stuck using Mouse forever. I look ahead a few years and see that becoming a severe limitation. A side issue is the compile time performance. While XS fueled Mouse is the fastest OO implementation, compile time appears to be most critical to Perl test suite performance. So, uhh... I'm going to go do a bad thing. -- If you want the truth to stand clear before you, never be for or against. The struggle between "for" and "against" is the mind's worst disease. -- Sent-ts'an