An Interesting Study was just released today by O'Reilly/Bitcurrent which confirms exactly what we've been telling anyone willing to listen -- Rackspace Cloud is upwards of 10x faster than Amazon's EC2 for Disk I/O and CPU.
Amazon's EBS solution is the big dog here.
(image property of O'Reilly -- read the full article here)
Everyone who knows Rackspace usually has two comments about them -- "Fantastic support" (they brand it "Fanatic Support") and "Expensive". With their Cloud Servers offering, they're putting the final nails in the coffin of the "Expensive" comment.
We've been hosting multiple domains (including this site) on their Rackspace Cloud (RSC) Servers for several months, and I could not be more pleased. You still get the "Fanatical Support", unlimited 24x7 Chat & Phone support, and you pay a whole lot less... for a better product.