Giant Freakin Robot has the pretty good synopsis.
I'm of mixed feelings about Enterprise. It always seemed to me that the writers didn't care about established Trek canon ... and worried about it all at the same time. For example, the show's very premise violates everything we'd learned about Trek and the Enterprise. I mean, the ship -- "NX-01"?? Since when? And who the hell was Capt. Archer? In the show's premiere, Earth/Federation history with regards to the Klingons is altered from what we know. On the other hand, when Archer is trapped in the past with the time-traveling Daniels, the writers seem to go out of their way to establish the canonical Earth-Romulan wars. The list is endless.
Nevertheless, BFR's Josh Tyler makes a good point in that the show's right-from-the-bat weakness is that it established time travel as the main plot device. Of the entire show. I'm a HUGE time travel aficionado, but even I saw that this was pretty weak -- and left too many "easy outs" for the writers if they needed 'em ... or, would allow them to just complicate the living sh** out of Trek canon even further. Honestly -- when news broke that the series was canceled, I seriously thought the whole Temporal Cold War stuff would act like the "Dream Season" of Dallas in which the whole series was erased from history.
And this all doesn't even address the insanity of dedicating an entire season (the third) to searching for a doomsday weapon. It gave "boring" a whole new concept.
As Tyler notes, the series seemed to have gotten its act together in season four, its last, but by then it was too late. It quickly (and very neatly) did away with the Temporal Cold War, and began to concentrate on story above all. Possibly the best episodes of the entire series were the "In a Mirror, Darkly" which used the long-established "mirror" universe (and, ironically, time travel) to tell an incredibly good story. But, alas, in the rush to tie everything up while running out of time, the finale hastily "established" the Federation ... with the lame plot device of the Enterprise-D's Will Riker using the holodeck to "live out" a history lesson.
But hey -- does any of this all matter, though? Star Trek has been rebooted, existing now in an alternate universe. Yeah, I know the Trek universe proper still exists (and many cool stories can be told!), but will we see any of it outside of novels, comics and fan fiction?
I tend to doubt it.