Oh yes, I had forgotten about weak references. I personally don't have a use for them (yet), but I've seen a couple modules that use it which I couldn't install for that reason.

A built-in IO::Scalar is awesome! I use that pretty regularly, especially in unit tests. In fact, our co-branding code uses it extensively. Anything that makes it faster/easier/better to capture STDOUT will definitely be a win for us.