Disclaimer: I ain't a hardcore Trek fan, though it is growing on me. I'm late to the party as they say.
That said, Enterprise is the first series that I have sat down and begun to watch all the way through. I'm halfway into the 2nd season and while it does exhibit so many missed opportunities I don't hate it by any means. I like the characters, except for Archer who behaves like a child at times. Yeah okay I get it, he is supposed to be a wide eyed naive explorer. A symbol for our species at that time. Still, he is constantly putting his ship and crew at risk when he makes some of the decisions he does. Just down right careless at times.
I like T'pol the most, she reminds me of Data in the sense that she is always at odds with understanding human nature. She is adorable at one moment, sympathetic the next. Perhaps not surprisingly, the only one who appears to exhibit any common sense at times.
I heard that the series really picks up around the 3rd season which is sad because it was too little too late. I also hear that it ends on a real sour note. This show had no business on UPN, the same network that brought us...."Homeboys in Outer Space" (really that show was offensive on so many levels independent from it being borderline racist). Hell the show was doomed the moment the pilot aired. Just a complete demographic incompatibility.
Note: Pardon the rambling, disorganized post. Just thought I'd give some first impressions.