Pros
Rare opportunity to get paid to work on genuine open source projects. Some very smart people. Most customers are smarter than average too. Some technical staff are given huge latitude to pursue their own paths within open source communities. The bureaucracy is present, as at any large US company, but rarely gets worse than a bit of benevolent clumsiness.
Cons
The company is deeply divided and siloed between the traditional RHEL product and the myriad other product lines brought in via acquisitions. There are continual management initiatives to try and build bridges but they're usually of the "pointy haired" variety and go nowhere. Every 6 months there's a new "common framework for X" project, and another such project quietly dies. There is a culture of cheapness, from placing offices in lesser-known towns, to constantly delaying salary cycles, to even asking some staff to share hotel rooms. Groups that are supposed to span the silos, like docs and testing (which red hat insists on calling "QE") are weak -- the docs guys are good but too few in number, the testing guys are mostly junior hires who are given more work than they can reasonably be expected to handle. Basically, it's a place you can carve out a very comfortable and interesting niche if you want, but to do so you have to be able to tune out the sound of all the chaos and waste around you.