Pros
IST is a relatively new and quickly growing contender in the managed services industry. Red tape and bureaucratic nonsense is practically non-existent, which helps foster a truly entrepreneurial environment. You can learn a lot about this industry quickly from smart people with experience and great ideas. Internal promotion isn't just lip-service here, the corporate office is full of VPs and other senior mgmt types who started off entry-level. There is a long and legit career ladder to climb and you don't have to have an MBA to climb it. Corporate provides programs for employees which reward and encourage high performance. Management remains intimately involved in site-level operations. IST's technology is it's best selling point to new customers. I've been in the industry awhile and worked for a very respectable member of the competition and IST's "stuff" absolutely blows everybody's else's out of the water. The software and systems I learned about during my interview process were the primary motivator for my choosing to join the organization. It is truly first class and cutting edge.
Cons
It's a young and growing company, so there are growing pains, but nothing that would make me advise shying away from a career here. Nothing worth doing is easy!