I finished my binge watching of ST:ENT and, for the most part, I liked it. There were a few episodes that seemed to be leftover ST:TNG scripts but the whole of the series makes up for it. Watching all of the episodes in a marathon fashion it was also easy to see at what point exactly the producers decided to use T'Pol to bring in more male viewers. The last episode of the series was a bit surprising considering that major character changes like that usually happen mid-season to help bring in ratings, not the literally last episode of the show.
The 'mirror universe' episodes of In a Mirror, Darkly were handled quite well. Personally I think they wasted S3 on the Xindi story arc, which itself was wrapped up rather quickly & oddly at the end, and could have spent more time with the mirror universe.
I lost count of how many times intruders were quite easily able to make their way onboard the NX-01 Enterprise. After a while the sight of an intruder became expected rather than surprising. Oh, look, a ship is approaching the Enterprise.... and there's the intruder.
I'm glad I went back and rewatched the series with a fresh mind as there were a few really good episodes in there and I was able to take better notice of all the references, some minor & others blatant, to both ST:TOS & ST:TNG.