1. I don't plan on using the on camera meter. I handheld meter. If I were to use an on camera meter then I would would probably want autoexposure too and opt for the OM2n, maybe the OM4Ti but I am not so familiar with this camera. Anyways, metering is not the issue.
2. I want a fast wide angle prime. And the 28mm f2.0 as someone else as mentioned is 49mm filter thread. The annoying 55mm filter threads of the 28mm-85mm lenses are the 35mm f2.0 and 50mm f2.0 lenses. I want the 50mm, but not so much the 35mm. Anyways, I shoot low-light often or I'm caught indoors with ISO 100 film. I can perhaps carry a second body for ISO 400/ISO 1600....but the 28mm f2.0 isn't as highly priced as some of their other lenses. I see them go for $200-$300 which isn't so bad in my pinion, but the 28mm f2.8 are much cheaper.