I watched Enterprise some, and I thought it was generally quite good. At some point the whole time travel thing just became too ridiculous for me and I lost interest. I think I always have a preference for TOS because I watched it when it was fairly new and it was a big part of my childhood.
there was a temporal cold war that was the backdrop for the whole series. it was an interesting storyline that spanned most of the run. all of the time travel related to that. the Enterprise crew was a pawn.
there was also a later storyline about the Xindi which paralleled the events of 9/11. they were manipulated into attacking Earth by one of the factions in the temporal cold war IIRC. they were basically told they had to stop earthlings from traveling the stars because in the future, earthlings would destroy them.
the end of the show was a big letdown for many, but once it hit its stride after the first season or two, it was interesting. worth checking out again. i think it was cancelled prematurely due to Star Trek over saturation.
http://www.startrek.com/article/poll-reveals-changed-perception-of-enterprise