I agree on grammar and homonyms - definitely a pet peeve. Typos can happen anytime, but that's what a good beta is for. Same goes for characterization - if you wanna be OOC, give me a damn good reason for it.

Also, if someone doesn't do empty lines between dialogue and/or story text (the BR html tag) - it's fine in books but it makes a text almost unreadable on the screen.

As for pairings. I can easily see Garcia/Morgan, Morgan/Reid, maybe even Hotch/Rossi, though my fave is Hotch/Reid.