SLR-wise, I have an extensive (3 film, 3 digital and 12 lens) Nikon system and a somewhat abbreviated, but serviceable (OM1n, 5 lenses) Olympus system, and have previously had a large (3 bodies, 7 lenses) Canon FD system. I state this to qualify my opinion as one who has first hand experience with Olympus
vs it's competitors at the time Olympus' OM system was new.
I have not encountered any camera or lens construction issues that would suggest that Olympus' quality control lagged behind either Canon or Nikon's quality control. After using my OM1n from 1985 to 2009, I found it necessary to send it to Camtech for service. All of my Canon equipment was stolen in early 1985, so I cannot comment on it's durability, but while I owned it, it worked fine. I bought my Nikon FG used, and replaced the foam rubber, and cleaned the optics. A Nikon lens developed leaking oil onto the diaphragm leaves, so that the lens no longer stops down correctly. All of the auto-focus Nikon bodies are working fine without service, although the N80 has a broken mode dial, likely from a bump, but operation of the camera is not affected.
The lenses on all of the cameras, save the oil-bladed Nikkor, function well within their specifications.
... What other systems in the same price range should I be looking at?
I see that you have already selected an OM1. It's a good camera, I really enjoy using it. It is sturdy and well made, and somewhat quieter than the Nikons I also use. The things I miss with the OM1n is more versatile internal metering, and any sort of autoexposure. When I want AE, but still want to have a similar experience (small camera, manual focus, etc.) I use my (now completely refurbed) Nikon FG. When I want auto-everything, perfectly done, I use my Nikon F5. Then I get a bit of upper-body exercise too!
Olympus lenses are quite good, although I have never done any 'testing' on them. I like the way photographs I take with them look. The selection is a bit thinner than Nikon's but it covers any focal length range I would want to use, often with a choice of apertures and other features.
The selection of Nikon lenses is phenominal - more lenses are available than any other system. But they are also more pricey than other slr lenses, due to the fact that nearly all Nikon cameras - even brand new digital cameras - are directly compatable with most Nikon lenses. This is not true with Olympus Zuikos, which can be adapted to a variety of cameras, including digital Olympus cameras, but they are not fully functional in this configuration.
Canon FD cameras and lenses are orphaned just like Olympus. They are not 100% compatible with modern Canons, but they can be made to work. FD lenses are very affordable, and there are a lot of them available.
So it mostly comes down to ergonomics - the costs will be similar for all three systems. If you like the left-handed shutter speed arrangement of the Olympus, it is the only way to go. If on the other hand, you prefer the Nikon/Canon (and Leica, of course) top-of-the-camera dial, look elsewhere. All three slr systems focus, change aperture and load film similarly. The metering systems are different, but they all work.
Congratulations on your new camera.