It's an absolute blast. They even have a podcast and broadcast some games on youtube. I'll leave a link to give you an idea of the level of play. I wouldn't call it beginner because I guess the former beginners have now been playing for years. Don't let that scare you though because the true beginners (sounds like that doesn't fit you) improve so much as the year goes on and have a great time anyway.
I've heard they are thinking about splitting up the D league into an actual novice league and those not quite ready for C league. The problem seems to be finding ice time because the league is growing beyond Des Moines' arena capacity.
https://www.youtube.com/channel/UCALiNu6nRMutwnxH1n1RpBg
I quickly skipped through one of the games and I think I would be fine holding my own. I'm a pretty strong skater as I used to aggressive inline skate growing up (during that short period when it was cool).
I'll probably try to sign up for the Fall/Winter league. I just need to start collecting equipment as I have nothing.