Pros
Working for salesforce.com means you are participating the build-out of the next wave of computing. The product is startling in its capability, quality, technology and elegance. The culture is young, dynamic, can-do and constantly on the move - very innovative and always looking for the next place in the market to be. It's energizing. The location of the offices, in downtown San Francisco, make it a great place to work (contrast with the usual Silicon Valley bunker-like low-rise in an industrial park). I had highly flexible working arrangements (work from home, flexible hours) but I know that is not available to everybody.
Cons
A very young, aggressive, smart and energized workforce has its downside: intense politics. If you are not in the right place or plugged in with the right crowd, it's hard to get ahead. Socializing after work is important, and if you are not into that or can't because of a long commute, then you can't network. You may just end up left on the sidelines.