I always liked his playing on the first OSI album
I almost completely forgot about OSI, but yes, the first one is the best, IMO. It's really the only OSI album I go back to anymore, despite owning all four albums and the Re:Free EP. Don't get me wrong, they're all good albums, but the first album just has more of what I like musically speaking, and I wish the project had continued in that direction with Mike/Jim steering the ship.
Regarding TWD, I woudl comment, but I've only really listened to the first album and while it was enjoyable, it wasn't quite my cup of tea. If you like modern hard rock bands with great musicianship, it's definitely worth checking out, but if you want prog, I'd say even Flying Colors is more prog. Neal Morse/NMB and Transatlantic are where you'll find Mike's most proggy drumming moments, though if you want something a bit more progmetal/metal inspired, Sons Of Apollo is a place to start, and they only have two albums out so far.
-Marc.