To me, the Xindi War was the point where I lost interest. It was just going back to what ruined Star Trek in the first place. As Guinan put it in "Yesterday's Enterprise", it's not a ship of war, it's a ship of peace. And Enterprise just HAD to go and pull a blatant Dominion War rip-off just when they were getting good on their own, didn't they? I'll say again, Star Trek is NOT about war, it has NEVER been about war. The only time war should be in Star Trek is if it is in an alternate dimension or if another species is at war, and the Federation is trying to make peace. Star Trek VI did a terrific job of portraying war in Trek. Enterprise just came off as depicting a bunch of redneck right-wing warmongers who "have to go get the terrorists." It was a poorly concealed metaphor for the September 11 attacks. In light of that event, Enterprise should have instead depicted the crew recollecting about how childish war is, instead of going to war themselves.
Sorry for the rant.