Thanks for your reply and suggested websites. After posting my message I too set out to locate websites, and found quite a few. As you pointed out, Amazon has quite a few models available. Googling led to many options and information.
The article comparing Fotodiox and Novoflex was interesting. The $20 Fotodiox seems like a good choice, but the $120 model includes an autofocus verification chip. Question is, is that feature worth an extra $100? I have several Novoflex items and they are very well made and durable, but quite expensive. However, I could not find a Novoflex adapter for Olympus OM, so it's not an option for me, regardless of price.
The most prominent complaint from reviewers seems to be concerned with the lens fit to the adapter. It can be either too tight, or too loose. Some report making shims to correct the loose fit. What a pain! Apparently the manufacturing tolerances may not be that precise. You might luck out and get a good fit, but maybe not. A bit like buying a third-party lens.
At this point I'm leaning toward the $120 Fotodiox model with focus verification chip. Maybe it is made to more exacting tolerances??
Thanks again for your feedback.
Below is a list of website I found that may be of interest to you, or to other readers - although the emphasis is on Olympus OMhttp://whitemetal.com/olympus/om_to_EOS_adapter.htmhttp://photonotes.org/articles/eos-manual-lenses/http://www.nobell.org/~gjm/photography/omadapter/index.htmlhttp://www.bobatkins.com/photography/eosfaq/manual_focus_EOS.htmlhttp://www.mir.com.my/rb/photography/hardwares/classics/olympusom1n2/shared/zuiko/index.htmhttp://diglloyd.com/articles/ask/lenses-LensAdapters.htmlhttp://en.wikipedia.org/wiki/Olympus_OM_systemhttp://forums.dpreview.com/forums/read.asp?forum=1029&message=31611910http://www.dvinfo.net/forum/canon-eos-7d-hd/480970-olympus-om-zuiko-mc-auto-s-adapter.htmlhttp://www.fotodiox.com/product_info.php?products_id=516