Wife and I have marathoned it over the last few weeks. Overall it has some really good moments.
Season 1 - Pretty terrible Overall, but sets up season 2 . The lead cant act, but is so bad its kinda corny good if that makes sense? Jackson's character grates on my nerves with his horrible acting also. We keep watching because of Coach and Stiles honestly.
Season 2 - Quality majorly picks up, production value increases a TON, characters really come into their own. Much darker also
Season 3.1 - Even better than season 2. Really love the Isac character (any Originals fans will instantly take to him, as the actor left teen wolf to be in Originals)
Season 3.2 - VERY VERY Good. Stiles (the guy we are talking about here) completely and utterly destroys all the other characters in the show. This kid can act and these episodes prove it. Also I was supremely happy they got rid of a certain annoying character at the end of this season. Good riddance!
Season 4 - So far terrible.
If there is one thing the show proves its that Dylan O'Brien can act and would be a great Spiderman