I use ec2, but would like something with lower network latency. However, this is a general comparison, so feel free to discuss based on all aspects of your experience.
I've only used Rackspace so far, so just providing my feedback for that.
Rackspace is cheap, as far as on demand goes. It's very easy to load up a server, configure it how you want, then save off an image to restore later. At high traffic times, the creation and save seems to take a bit longer.
Latency seems to be a little on the high side. Simple comet js pushes take a bit longer than they should, and outgoing queries are also similarly slow (i.e. sending out a request to someone else's API). Inbound standard traffic seems speedy enough.
Rackspace is cheap, as far as on demand goes. It's very easy to load up a server, configure it how you want, then save off an image to restore later. At high traffic times, the creation and save seems to take a bit longer.
Latency seems to be a little on the high side. Simple comet js pushes take a bit longer than they should, and outgoing queries are also similarly slow (i.e. sending out a request to someone else's API). Inbound standard traffic seems speedy enough.