I've used DO in the past for quick spin-ups, and they're great for that. But for long running applications I'd stay away. Was actually considering DO for a new project, but this kind of tipped the scales the other way.
If you're looking to switch, I think Linode gives you the best bang and reliability for your buck. Have also used Rackspace for a previous startup. A bit more pricey, but also a great service if you're considering switching.