I personally never was that found of the intro song, to me it sounded too much like a bland rock song from the 80's. But it's interesting that they were trying another approach from the classic instrumental intro songs (which I like better, though). And the visuals' optimistic theme were great during the song. I like the idea, but the song unfortunately does nothing to me.
I really liked though in the Mirror episodes, when they temporarily changed the optimistic concept of the development of ships and planes that finally makes it into rockets that explores the space, to a dark tune with pessimistic scenes of war machines instead. It really sets the tone to these episodes.
Other than that, I really enjoyed Enterprise. It seems to be somewhat hated, or the least popular ST show, but I had great fun watching it. Of course it had bad or boring episodes, and the first season is the least favourite. But those subjects goes for all ST shows, and is part of the charm with the Star Trek universe IMO (perhaps TOS is the most even show in that matter?).
Edit: Yes, the ending was bad.