Well I really enjoyed Season 3
While not as edgy or humorous as Season 1, I think Season 3 is overall the strongest season to date. Like the first season it has jokes, but unlike the earlier seasons it also has pathos. It also built more consistent character arcs, which while slower, ended up leading to a powerful payoff. E12/E13 had some great moments - Paul telling Lindsay to 'lawyer up', the slow bleed of Jimmy's enthusiasm after Gretchen mentioned the word 'family', even the rise of Edgar to a normal, successful person - all of which wouldn't have had nearly as much depth or resonance if the show had stuck to its Season 1 format.
The show is changing, maturing (although maybe that's too strong a word), and Season 3 is the epitome of what good, unrestrained sitcom television can accomplish. Looking forward to Season 4.