[Ask /r/SysAd] IaaS recommendations?

Hi /r/sysadmin,

Does anyone here have any experience with Infrastructure As A Service platforms (virtualised datacentres)? I'm trying to compare them, and based on what little information I could find about them, there doesn't seem to be much to set one apart from another. Are there any which really stand out - or any to steer clear of?

Thanks!

Edit: To clarify, I'm looking at IaaS platforms (eg, OnApp, Cloud.com), not IaaS/PaaS providers (eg, Amazon EC2).