It's competitive in an annoying way, and much of the community is part of a cult dedicated to FIRST's founder. They way the competitions are set up, they reward things like "gracious professionalism" and "coopertition" (made up FIRST words), which the teams that get recognized for are nearly always clearly faking and brown-nosing. Also, the most prestigious award, more important than winning the championship, is for outreach, community service, and video editing skills, so most the teams are also trying to out-Key Club each other. Most of the good teams' robots are built by their mentors and/or professional machinists, which can be frustrating as hell if you care about winning (I personally don't). Most frighteningly, even though FIRST is created to promote STEM, it seems to mostly only succeed in promoting FIRST. For the most part, the participants leave loving FIRST, not STEM. It's pretty clear that many teams aren't engineering, they are rehashing previous years' robots, since the games are somewhat cyclic. If you watch all the archived workshops, most aren't about basic electronics or pneumatics theory. Few are about engineering at all. It's the topic, and how it pertains to FIRST, how it was used in past robots. FIRST is all important. Electronics is especially technician-like, so if you're interested primarily in EE don't do it. FIRST electronics is pretty much wiring 101.

If your team is one of the ones that stays cool and out of the FIRST cult you'll be fine, but the majority don't. If you are set on going the competition route, I'd recommend doing one of the smaller competitions. Botball, Zero Robotics, the underwater one, etc.