Pros
Where else can you be a part of setting strategy for your clients? Direct access to CIO's and executive team, with the ability to really make a difference and bring value to every meeting because of the excellent analyst community (i.e. 'product') that Gartner offers. I work from home, manage my own schedule and my boss is not at all a micro-manager. He expects a strong work ethic and excellent results, and he gets it.
Cons
At a corporate level, I have some concerns with how Gartner manages clients 'geographically' as it creates situations in which you are competing against your peers in other regions; also with executives maintaining more than one office it is often not clear where 'home base' is, which means everything in terms of how the growth is recognized and how that client is managed.