So why pay $150 for shared hosting and a cpanel?
It's actually a cluster of load balanced servers with shared storage served via NFS. The database is on another server which is setup with MySQL replication to a slave for disaster recovery. The email is also served on separate servers. If that isn't enough, there's also a SSL cluster in-front if need be (additional $20/month for SSL I think the rate is). Be aware though, no SSH access and no executables will run either. However, there are cron jobs.
They've recently upgraded the web stats system which has seemed much more stable but of course you can just hook up Google Analytics or process your own logs. Their support is great with about 5-min response (at night) but usually 1-minute response times for their online chat (I haven't used the phone support).
While you're at it, you might as well check out Cloud Files and its CDN ability served via the Limelight Networks.
Check out their wiki/KB if you're looking for more info: http://cloudsites.rackspacecloud.com/ and be sure to compare SLAs and Terms with other shared hosting providers you're considering.
(FYI I don't work for them :P)