We have several servers with Rackspace, and we've been with them for well over a year now. Here are my ratings:
1) Reliablity - 10/10 - They've got VERY good uptime and support, they use only high quality, branded server parts.
2) Cost - 8/10 - Rackspace don't get top marks here as a lot of people would say that they are costly. But you do get what you pay for, and it's well worth it since you get great uptime, support and reliability from one company.
3) Additional cost (backup, bandwidth and etc) - 9/10 - They've got anything else you want extra basically... just ask for it.
4) Support - 10/10 - There's always someone there to answer your questions. They have real 24x7 telephone support and they constantly answer support tickets.
5) Uptime - 10/10 - They've kept their network uptime to 100% over the past year or so which is very impressive. Server uptime is another matter, but our servers have been up for more than 99.999%. The reason the server hasn't had 100% uptime is due to rare Apache restarts each month. But our servers have all got more than 100 days of uptime, with 172 days of uptime being the longest.
6) Performance/Speed - 10/10 - Very fast and reliable network.
7) Ease of use - 10/10 - They've got a contorl panel that you use to manage your account and servers with. So one login to manage all servers... you can check bandwidth, invoices, support ticket status etc.
8) Terms and conditions - Not too sure how to rate this, their terms and conditions are standard, more or less the same as other hosts, no adult materials, no spamming etc.
Just my thoughts on Rackspace .
Former Systems Administrator