It's not my favourite series, but my opinion of it has radically altered over the last few years. I was 17 when the show first came out, and I was in many way a stereotypical cynical teen. I didn't evaluate the show on its own terms, and instead complained about all the things that I thought it should be. To my regret, I was the worst sort of whiny, proprietorial 'fan'.
Lately though, I have been rewatching all of Star Trek via Netflix, and have come to enjoy a lot of Enterprise, if not all of it.
I find the crew likeable and very relatable - unsurprising considering they are closest to our time period out of all the Trek shows. I love the movie nights and baseball caps - small touches like that go a long way.
Even when the show was utilising a well worn Trek plot, the show had a unique vibe that came from the fact that the crew weren't experienced explorers, at least not initially. I also like that the NX-01 is clearly inferior to many of the ships it encounters.
The show is extremely well thought out, visually. The exterior looks primitive and metallic. There are tons of little details on the cg model that give it a cool mechanical look. The interiors, if anything are even better. As has been mentioned, they have a submarine/ISS mashup sort of vibe, which is perfect for the period. Same goes for the uniforms, which might just be my favourite of all the Trek series.
The Xindi arc worked well, and gave rise to new storytelling possibilities and character growth.
T'Pol is my second favourite Vulcan after Spock. I think she's a brilliant character.
Season 4 tied the show nicely into the wider Star Trek universe. Some people find it too fan-service-y, but I love all the little nods to other shows, and never found it intrusive to the plotlines.
I have a lot of time for Enterprise, and find it extremely watchable.
