Pros
Free/discounted flights for standby travel may be the best benefit a job can give you. If you're into travelling, this is a great place to work. Medical benefits and a unionized workforce make this job pretty good for anybody trying to make ends meet. You can work virtually as much as you want and potentially as little as you want (but that takes quite a bit of effort), which is nice because the work isn't even hard. Simply meet the physical requirements and the rest is cake.
Cons
Management is a mess. I'm not only saying this out of frustration, it's objectively true. Seeing as I've worked here at SFO for 5+ years, I just assumed all airport operations were this chaotic. But after talking to employees who had previously worked at other stations (such as ORD, CLE, and IAH) I found that the unanimous consensus was that United's SFO Management is truly just incompetent and refuses to heed any advice that might better operations. It also doesn't help that they frequently try to intimidate you into submission. Another worry for all of us is how the company will repeatedly try to redistribute profits away from you, the employee. The most recent example was back in March when the company tried to do away with their profit sharing program (in which $30m-$80m of the company's profits were given to the workforce per year) in order to replace it with a lottery system (which saw only a select few employees get a rather large prize, costing the company a mere $18m a year by comparison). Fortunately, our strong and immediate backlash put a stop to that change. This company may provide many opportunities, but make no mistake: United Airlines does NOT care about it's employees.