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Thanks for the helpful response, Oleg. So far in examination, pretty much all of our ranking terms point towards a category page, whose URL would not change. While some of our product pages are indexed, very few seem to come up in SERPs. I still worry there might be a ranking drop on the overall site. We do ok in G for some terms, though not nearly as well as I'd like. I guess fixing other major issues should be a priority. I think we'll look at using canonical tags and 301's to correct the problem, at least in the short term.