Most of the pros and cons listed there still apply. In it's current form, Rackspace Cloud compute is little more than VPS with a few cloud features. However, the next gen Rackspace cloud platform will make significant improvements: http://www.rackspace.com/cloud/nextgen/
For now, EC2 is a far superior compute platform in just about every way.
The smaller rackspace instances tend to perform better than the smaller EC2 instances (anything below m1.large), especially in terms of I/O.
If you don't need the advanced EC2 features then rackspace is also more comfortable to use (real IP addresses, no messing with EBS).
This is true, I mentioned this as a pro in the quota post. However, the performance is relatively flat - it doesn't scale on higher instances. On the lower end Linode tends to perform better than rackspace cloud.
My point was that rackspace is easier to get going when all you want is "some servers" without building a lot of machinery upfront. They sell you a VPS, no more, no less, whereas EC2 exposes you to all sorts of magic that small deployments don't need.
I.e. automating EBS attachment (reliably) is non-trivial. That's a major hurdle on EC2 if you're not familiar with it because most EBS-backed instances are deliberately on small volumes, thus you usually have to deal with it from day 1.
Likewise the networking/NAT on EC2 is a royal pain in the ass for newbies and veterans alike. It's a poor design; public IPs could just as well be mapped directly, but as it stands anyone running on EC2 has to deal with that idiosyncrasy of the platform.
And finally, price/performance really is better on the small rackspace instances versus the small amazon instances.
As a rule of thumb: When you can get away with instances smaller than the 16G-rackspace then use rackspace (beyond that their pricing is even more ridiculous than amazon's). When you need bigger (or expect to need bigger in the future) then use EC2.
And before you pick either make sure to remind yourself that the cloud (any platform) only makes sense for small or large deployments. If you're in the mid-range of 10-40 servers then renting dedicated servers will be drastically cheaper in almost all cases.
FWIW, we run a mid-sized deployment on EC2 (~60 instances) and anything interactive has to go on at least m1.large and up (usually xlarge). We do use m1.small's for queue-workers and low priority batch jobs.
Not quite. You will get far better IO on Rackspace. Also, you get more CPU bang for you buck. Not all of us need anything beyond a highly performant VPS.
Except they don't offer a 256MB RAM option. Rackspace does, for $10 a month. The only other serious competitor in this space is the EC2 micro and well, it doesn't perform as well.
I'm not sure this is necessarily true. We did a recent study and found RAX costs almost double for our example web app: http://blog.shopforcloud.com/2012/02/holy-cow-rackspace-uk-c...