Dan,
to answer your initial question, I've had excellent luck with Amazon but not always with their 3rd party sellers -- as Preston points out.

As for the new 500D, technology rolls inexorably on and this is a block-buster, entry-level feature-set. Wow. If it weren't for the rather low fps (comparatively) and the use of SD cards, I'd consider it as a backup.

If price is your objective, the XSi will be an outstanding bargain. If state-of-the-art at an entry-level price is the objective, it looks like the 500D will be hard to beat.

Happy hunting!!

Jim