jdMorgan - 6:12 pm on Aug 6, 2010 (gmt 0)
Using all-lowercase URLs is not inherently better or worse from a technical, but it is certainly simple to redirect mixed-case or mis-cased URLs to all-lowercase URLs using a single rule than it is to redirect each URL-case one at a time using separate rules.
Using mixed-case URLs is almost begging for errors in incoming links, due to the facts that people may not spot all the uppercase letters or remember to type them that way, and the fact that folks are lazy, and just may not bother with that shift key. So the trade-off between "good-looking URLs" and having to correct errors in inbound links has to be seriously considered.
If you do implement 301 redirects to fix casing (or any other errors), be sure that all the links to your pages from within your own site are correct and do not result in a 301 redirect. Redirects can be used to 'fix' bad links from other sites, or to speed search engines' re-indexing your URLs, but should never be relied on as part of your site's normal operation.
Note also that Apache servers are case-sensitive, while IIS servers are not.