I thought it was a pretty good series, but nowhere near as great as I see some people make it out to be. I loved everything up until the end of the Girl A arc, after that I just sorta watched on and off until Tereui came in and really saved the series for me. It felt like things were getting into motion at last and actually becoming a bit more interesting than everything that had come before it. I wasn't the biggest fan of Shotaro as a main character, but I did like his character decently enough after a while. The story towards the end was a little random with Foundation X, and since it leading into OOO was just a joke, it makes me look at it a lot less favorably as some grand connector and more like just a pointless addition to the story. The series could have been done just fine without the addition of Foundation X.
Though for all its faults, I still say it's a very fun series to watch after a certain point and has kept me more interested than OOO, which I sadly dropped.