Peter

@stakx I haven't implemented any caching mechanisms myself, I just fixed the way expressions are compiled for It.Is, [see here](https://github.com/moq/moq/commit/3569b288db0ef9b8cd3af6fb1fbac70f5fbb1c3e). This already fixes the biggest performance drop that causes times...

@stakx I was also thinking about the same thing, but I can't see anything that can become an issue here, since nothing is captured in the scope of It.Is, all...

Ah, completely forgot about this one, submitted #1512. It's that same fork I used back when I created this issue, but no conflicts it seems