Generally it's not to bad of a time commitment in my opinion, like an hour a week until play offs where you play multiple (if I remember correctly). If you're captaining a team, it can be hard to get a full team to commit to a time slot especially since you don't get to choose what day you all can play, only the time and that's if you can get a full team on imleagues to accept the invite onto the intramural team. I had some troubles where the games would be on Friday afternoon/evenings and it was hard to get a full team to come out to play due to class commitments and because IM didn't fit into their Friday night plans.

As for competitiveness/skill range, I can only speak for Ultimate but usually pool play isn't competitive unless you have a team with club/exclub/experienced players in your pool. Otherwise, when you're in playoffs it gets much more competitive because the teams who have experience playing ultimate obviously make it out. The majority of the teams playing don't have much experience and play for the sake of playing and being active.