I like the series, but its gone a bit downhill since Noah Wyle became a big part of it. In season 1 he was barely there (I think because Falling Skies was still airing), so we got a show focused on the other characters, and I liked it a lot. The second season became the Flynn show with everyone else taking a backseat, and while it was still pretty good it wasn't as good. Season three I still haven't finished. It had a terrible villain whose entire plan is basically incomprehensible, and its even more of the Flynn show even focusing on elements that are completely confusing if you haven't seen the TV movies (and I haven't).
If Noah Wyle could find another project I think the Librarians could go back to being very good. As it is, I'll probably finish up Season 3 sometime before 4 comes out (if it gets made). The show had a lot of promise but its lost a lot of it by taking away a lot of the elements that made Season 1 so enjoyable for me.