Hi -- New here, but I just won an OM-2 in a local online auction along with an OM 24mm 2.8 lens. I really just wanted the lens b/c the camera looked far too rough. But, I got it home, cleaned it up and it's awesome! I also have an OM-2SP, an OM-4, and an OM-10 FC. Do know that it'll seem locked up until you put a couple of good batteries in it. The film won't advance, shutter won't trip, etc. without good batteris (2 SR44's). The only other thing I've noticed and read about is that Oly used foam strips in the pentaprism much like the foam light seals on the body. And, just like the body seals, the pentaprism foam breaks downa and gets gets nasty as well. When I look in my OM-2's viewfinder, I can see a small piece dangling from above. Problem is, the foam goop can get on and stain the pentaprism, causing permanent damage. So, it's recommended that you carefully remove it all or have a professional do it. It's not needed to replace it; just remove it.
I am sending my OM-2SP off to get the missing collar on the rewind button replaced, but after that's done, I plan to send off my OM-2 to get the pentaprism foam issue fixed. But, it's a tank of a camera, yet small eough in your hands to be comfortable. If you do get one, find one w/ the detachable shoe. They add $15-$25 to the price of the body if you have to buy one separately online. Not terrible. But, you don't pay extra for one when you buy it on the body. So, save yourself the trouble.
Lastly, I've noticed that the glue keeping the body's leatherette coverings isn't the best and tends to lift at the edges. Not a hard fix, but you might find a great camera that looks a little ratty due to this lifting. Don't let it deter you. Re-gluing them is an easy task. If you haven't already bought one, good luck...