I found it hard to sit through, honestly. It had that vibe that sitcom pilots often do, where you're not really sure whether this show can be funny or not, because they're introducing characters and settings and stuff. It felt like an uncomfortable mix of "hey, we're back and nothing has changed" and "this is a total relaunch, so expect everything to change"
I also found the "Abed" thread of the episode confusing and cringeworthy. They were clearly trying to tie his happy place version into the "real" version at the end, but it didn't actually come together in any sensible way. And it wasn't particularly funny. Not having really followed the breakdown of the show, and Dan Harmon's departure, etc., the only thing I can think is that Abed's happy place version of the show was a way of poking fun at the skeptics by deliberately saying "is this what you thought we were going to turn this into?" But it doesn't make sense that Abed's happy place isn't, well, happy at all.
I'm sure I'll give it a few episodes to find a new stride, but there's plenty of better comedy on right now, and with several of my other favorites returning this spring (Game of Thrones, Doctor Who), it'll have a lot of compeition for my attention.