Amazon AWS

• User Interface: Poor, mostly confusing for simple tasks, AWS runs cloud but their own login interface is odd and bloated, each service has too much options shown to the user and the services are not bundled together. Only good thing is there are preloaded AMI instances which saves you time to start from scratch
• Support: Confusing and too much clicks to get to any help
• Products: Too much products, S3 / Elastic IPs / yada yada. Do we really need to know that? Get a virtual machine instance up and thats it, others are option or specialists extensions. No simple quick one hit option. Typical talk too much too little done.
• Cheapest instance is Micro Linux EC2 at $0.02 per hour

RackspaceCloud

• User Interface: Straight forward instance creation that is painless. You can install your preferred OS. Very nice interface which is simple and clear.
• Support: Live support and phone in support at the click of a button. Beats amazon hands down.
• Products: Limited to Cloud Files (vs S3) and Cloud Servers (vs EC2). Less things means more time to focus and make them better. Bad is too less options, but this can also mean a good thing.
• Cheapest instance is 256mb at $0.015 per hour