I recently switched all of ~100 my domains to Namecheap. My reasons:

• Good prices (make sure to ask for the volume discount if you transfer a lot of domains at once)
• Availability of most .TLD's you'd need
• Website is relatively easy to use
• Not too many up sells (unlike GoDaddy, etc)
• Good customer support (haven't needed it much, but when I transferred all my domains to them they were extremely helpful making sure everything went okay).