We (Mike Cressman, DB and I) climbed the south gully on East Mary. Mostly a loose scramble, there were two very short 5th class pitches. Nice views and great company. I'd call the route 5.4.
While my partners hung out on the summit, I went over to Middle Mary. Again, mostly a scramble but with one 5.2 (wet - snowmelt) chimney halfway to the top. I avoided it on the descent and found a spicy 5.2-ish downclimb with exposure nearby.
Looking over at West Mary (the highest of the Three Marys) from the summit of Middle Mary, I didn't see a reasonable way up. Looked to be sustained upper 5th class.