Pros
What stands out about IMC is the smart people you work with, the quality of the projects, and the learning that you do when you are there. I have met some great people that work here and they stand out compared to other organizations where i have worked. They have great perks -free lunches, etc. and there is always something social going on.
It's a cool combination of fun, while maintaining a level of seriousness about the work that gets done.
Cons
If you have any vertigo, the office may not be for you - the 43rd floor of the Sears Tower makes for a great view, but my girlfriend can stomach it.