Ive used Send Grid for mingletrips.com. Works great. We are going to use Amazon SES since we are hosting the next app on EC2. Will give my feedback on SES.
Awesome service! Blows away the incumbents and has mobile monitoring apps! You MUST try it!
Elastic Email is the lowest cost provider on the market and they provide a complete solution at that price. Can't be beat.
Incredible deliverability and customer support!