I'd say it's been rather pleasant to be hosted at rackspace cloud, the support is second to none, just as they have always promised.
The only thing I have to be picky about is the uptime - they are not the best among all the hosting providers I've dealt with. A few intermittent down times across the months have been detected. Nothing major but still.
Overall they are a very unique company with unique approaches that's worth the money if not your mission critical websites. Go with Rackspace managed hosting instead if you are looking for absolute reliability and accountability.
4.5 / 5 from me.