Hi -
My Om 4 is my second Oly, my first is an OM 10 with f1.8 and everready case I scored for $27.50 at a second hand shop which didn't know that without batteries nothing works. Works fine for me, I added the Winder 1 the Manual adapter, and the T32 flash. Nice little outfit. The other day I bought the 4 with a 28mm f2.8 with a stuck filter (the 28 was "free") in clean user condition - no dents, only a few scratches and a little worn paint. The 28mm looks just fine, snappy diaphragm, no scratches, etc. Gotta get that filter off!
The 4 is I think the early version since the battery check runs and runs and.... I've bought the instruction book and a f3.5 135mm, sadly it has to go back since the lens latch won't latch. Alas!
Any suggestions or cautions based on user experiences? Battery life? I've found no mention of mirror lockup, a surprising omission. New seals from Jon Goodman should arrive soon, and I'll be up and running.