robdwoods - 5:50 pm on Aug 6, 2010 (gmt 0)
My main site has tons of 301 redirects on it due to some poor architecture I inherited and later fixed. A significant portion of our links are 301 redirected and our rankings since Mayday have actually improved significantly. I don't think there has been any devaluation of 301's from Mayday, at least there are no signs of it on my site that has a lot of 301s in our link graph. We have more #1 and #2 rankings on competitive terms since Mayday than we have ever had.
We use the mixed case URLs as you do eg. www.example.com/Product-Category.aspx and 301 the all lower case versions to the mixed case version.
We both redirect non-canonical case versions to the case version used on the site and have implemented the canonical tag to capture any other non-standard URIs that may have been linked to.
We use 301s wherever there is a good chance that a URI may be linked to and the canonical tag is essentially used as a fall back to catch any that are odd enough that we wouldn't think to add a specific 301.