Pros
RS is very good to their employees on the surface. There are many perks, everyone is stoked to go to work, and it seems as though you're going to have a ton of fun on the job. In many areas of the company this is completely true and RS provides. They provide a very fun, relaxed environment that allows you to thrive if you're a self starter.
Cons
Management is becoming less and less "Rackspace." Over the last couple years the management team has become full of managers operating under the theory X style of management. They have driven many, many long term Rackers out, including the CEO. If management doesn't look to those leaders who have been around since the early days (those that are left) they're going to drive them away. I went from a die hard Racker to someone who was completely heart broken when I saw this decline... It is as if they don't ever know what the CORE values are.