Wow this thread has moved on a lot since I looked at it the other day. Will have a proper read over the weekend, but just to add my 2-cents on the changes to the Vulcans in Ent:
As I've said I liked what they did with the Vulcan's, having them as passively hostile and almost like a disapproving parent was in my opinion probably the biggest and best change made to the show (and not totally out of the blue, DS9's Take me out to the holosuite was a starting point to this), quite a bold statement to make but it's because it opened up so many doors for story telling and the episodes that focus on it are the one's above all others that feel like Ent and that could only be done on Ent with that set of characters.
As has been said, Archer being all hot-headed and a bit of an idiot makes sense when you consider his history with the Vulcan's and his father. Couple all this with the Andorian's in The Andorian Incident and you've got the got the setup for the best (IMO) ongoing storyline in Ent.
I'm not saying it was done perfectly everytime and I agree that the Vulcan's attitude came across as a bit forced and needlessly confrontational but compared to some of the other ongoing storylines in Ent and the other series it stands up pretty well.
Looking at it the other way, had they not changed the Vulcan's, and instead kept them as the boring, flat species they were in TNG, which is often (and mostly for very good reasons) put up as the golden standard to which everything is compared, then the show would have been much worse for it.