Pros
RIM has more or less taken over the city of Waterloo. This has a few benefits as lots of companies in the area (such as car dealerships) offer discounts to RIM employees. Of course there's also the usually listed benefits like you get to carry around your choice of BlackBerry (at least in my group you do) and there's lots of free lunches/ice cream/pizza/whatever all the time. The flex-time is also very nice. It would be pointless for me to show up at work at 8:30 since there's no way I'd be awake enough to do anything before 10-10:30 anyway, so being allowed/encouraged to work whenever works best for you is nice.
Cons
Growing way too fast. A lot of the 'team-lead' style management is a disaster. Feels like RIM's left hand doesn't know what it's right hand is doing. It's always extremely cold in the office and despite thermostats on the walls you might as well not bother changing them since they seem to be controlled from some other location and reset to 'freezing' every few hours. Due to the very social 'culture' it's occasionally hard to get any work done - people standing around talking loudly, playing with toys or just talking about how smashed they got on the weekend, etc... Headphones only help so much.