Ditto. I especially like that it's fully compatible with the existing http.HandlerFunc interface, which is a big deal. This means you can just write "regular" handlers as middleware (or bring them over from existing code) without having to reinvent the wheel.
I also very much like the way it leaves sessions up to you. A few other Go frameworks leverage http.Cookie, instead of letting you use something like gorilla/sessions. I'm a big proponent of server-side sessions (wherever possible) given how simple gorilla/sessions + Redis can be to set up.
I'm a little tempted to use this myself (I've been going mostly naked so far) for my weekend (read: also weeknight) project, given that all the "real" logic (middleware, DB queries, etc.) can be dropped in alongside it.