I used an FG through college and I'd like to get another for when I don't want to drag the motorized F3HP around. It's a great camera that's very easy to use at eye-level (I love the metering display on this camera!). I used the TTL flash for lots of work, including macro, with great results. It's not quite a pocket camera, but it's definitely smaller than the F100 (which I've also owned). The only major things missing on the FG are AE lock, DOF preview, and a PC connection for external flash sync. The first two are mostly convenience features in my opinion; the external flash connection is easily addressed with a $10 part. Unless your 50mm is a G lens (no aperture ring), it should be perfect for the FG.
Having said all this, I've also used the OM2n. I sold one once for a friend, and of course I tried it all out first. I almost bought that kit myself, it was very nice and I found the flash system perfectly usable. If you like it, get it!