The Temporal Cold War was a terrible idea to begin with. I hated it all the way. But the Xindi story was worse for simple rerasons:
First the whole story changed the impression Archer made on me. In the beginning he was merely the guy from Quantum Leap doing the Captain for me and I hoped his character would develop. But then came the Xindi and out of a sudden Archer talks about WMDs and how another 9/11 must be prevented and... well... now he was the guy from Quantum Leap doing George W. Bush. Stupid plus stupid often equals idiocy.
Second, I just got annoyed by all this Xindi Mafia Meetings. I allways expected one of them to raise his small finger to his mouth and laugh like moh ha ha ha ha!