Pros
transit helps so many people everyday and you are part of that great mission. you have talented coworkers and great benefits, vacation, etc (whether union or non-union). there are many opportunities to work with other government agencies in the metro region. the transit/transportation field has started to grow again (after the great recession), so you can gain great experience at one of the highest recognized transit agencies in the country.
Cons
compensation is insultingly out of whack with the market (above and below), despite "market reviews". it is still an old boys club and not just in the union departments. women managers are treated and compensated differently than men in the same/similar roles. no succession planning is happening, which is fine now, but will backfire when the imminent wave of retirements looms near. in recent years, there has been a hemorrhaging of millenials due to lack of upward movement. the "us versus them" politics between much of the union and management is painful and inhibits work from really excelling.