Vantaggi
The people and environment are what make Red Hat a great place to work. The company is chock full of incredibly intelligent folks and the majority of them are always willing to lend a hand. Benefits are on par with other companies I've worked for. Your stay at Red Hat is really what you make of it. If you become complacent and are okay with doing the same thing every day, you might not stick around for long but striving to learn and do more is really how you'll thrive.
Svantaggi
The company has been going through some growing pains the past few years. There has definitely been a shift from being the little guy leading a revolution to becoming yet another big company. The culture has suffered from it but compared to other places, it's not bad. You've got both sides of the spectrum now with die-hard FOSS folks on one side and employees who don't even fully understand how Red Hat makes money on the other with most people falling somewhere in between.