While every provider has their own merits/demerits, I personally feel AWS is growing and expanding at an exponential rate. Look at their products and services page and to see how many new services are introduced every day. They have a service for everything and integrating them is just plain simple(Basic day to day stuff's). Their pricing is also on the lower side. Close to 2 years now, and never see the bill cross more than 10$ and that too with medium traffic and lot of scheduler running. It took me just a week to get the site up and running with all necessary services like SNS, Route 53, S3, EC2 and ELB.
They just simply won't stop introduce something and for me, that is the right step towards success.