1. Rackspace cares about "Rackers" more than anything else. It is not just hype.
2. There is a strong "promote from within" atmosphere.
3. The company works "fanatically" at creating a culture where Rackers "Treat Each Other Like Friends and Family". This, more than anything else, is the main reason I could stand the Texas heat and still be working with Rackspace.
4. Great opportunities for training and skill development are everywhere.
Cons
1. It gets very hot in Texas.
2. Salaries are somewhat on the low end.
Exposure to a multitude of unique problems and situations. You will have to wade through an obscene amount of email tickets, but you will have those gems that stick out. You have opportunities to get industry certifications (RHCE, CMDBA, MSCE, CCNA, etc.) that will help you down the road.
Cons
I feel the culture diminished significantly when the company went public, though some irresponsible employees helped. If you're not working days, your workload will be significantly higher, despite the cited breakdown of servers per employee.