It's not necessary to use mod rewrite, but I like it

I prefer "http://www.domain.com/go/bilfhunter/" over "http://www.domain.com/link.php?id=2" because it slightly improves ranking for the link.php page in G (although granted sponsor tour pages don't really rank well at all usually) and it's more inviting for surfers to click, imo. Of course you can use mouseovers too, but I prefer "http://www.domain.com/visit/bilfhunter/" to show instead of "http://www.bilfhunter.com/."
Also, there's nothing wrong with the switch/case setup, but I have sites that use 2000+ paysite links, and for those, I prefer just having one php file with 2 lines of code.