Pros
I like the variety of work and the different disciplines (architecture, landscape, planning, etc.) that are all under one roof. It makes for some interesting cooperation between departments. I'm just out of school but have 3 weeks vacation, which not all companies offer. We also work a 37.5 hour week, which is nice. If you have something you need to do on a given day, you can generally get permission to do it, and just make up the time later. For a company with a professional office environment, I find them to be very flexible. All offices have politics, but I have found that to be less of an issue here than other places I have worked.
Cons
For me, the worst part is definitely the commute. But that is a common problem in most cities. The potential for something along the lines of profit sharing would also be nice. Sometimes a lower-paid employee like me can feel like a cog in the machine...again, a common problem anywhere (the "professionals" versus the "tech" level people). I don't hold this against the company, though...nowhere is perfect, and there are definitely more pros than cons.