I'm using the Korg NanoPAD to tap in two measures of something I'm looking for in EZ Drummer2, and voila; the search results spit out tons of examples based on what's in my library, sorted by relevance. It's like Google search for MIDI loops.
I dig. I dig a lot.
It's not bad. I don't really use MIDI files too often, so I don't have much cause to use it. But the handful of times I have, it's been pretty good (although it had trouble when I was trying to find a very basic half-time beat).