Enterprise's casting/characters was a mixed bag. I loved Malcolm, Trip and Phlox. And yes, even with his inconsistent writing, I liked Archer (because Scott Bakula). But T'Pol, Travis and Hoshi were pretty poor IMO. Still, I liked the cast much better overall than Voyager's cast. It was the lack of creativity in the story-lines and the ENT universe that really hurt it I think. It did feel too safe and familiar (in the first couple of seasons at least).
Having said that, I still like the series and think it's underrated. It felt like it was really starting to live up to it's initial promise when it was cancelled. Hypothetical Seasons 5-7 could have been some really great trek, just going by how the show was progressing and some of the ideas they had for Season 5. But we'll never know, sadly :-(