This is something that has also been a part of Trek from the beginning. Most people agree that the episode where Spock, Kirk, and McCoy meet up with a peacenik chick in the 30s is one of the best episode. Well, that was time travel. Trek has always had time travel.
This however, I've got some issues with. The Guardian on the Edge of Forever (was that the episode name, or merely the name of the gateway entity itself?) is an excellent episode not merely because of the time travel aspect, but because of the script as a whole and the performances in that episode. I do think that time travel has become something of a trap that the writers are falling into - heck, have fallen into. I (and many other Trek fans, I think) believe that it has been used far to often as a plot device.
On the one hand, it's a very easy to use - you've got the dual possibilities of familiar characters in unfamiliar situations (which can be used for either dramatic [Guardian] or comedic [A Piece of the Action] purposes), and you've got the ability to bring other familiar faces from the other ST shows in as cameos (I can't think of any obvious examples other than Trials and Tribulations off the top of my head, but I'm sure they're there). However, I think there are far to many problems with continuing to use this concept (and it's one of my primary worries with this 'Temporal Cold War' that seems to be an important, if so far barely touched on, premise of Enterprise).
A couple just off the top of my head - First off, is time travel easy or difficult? Depending on the writer's moods at the time, it seems to be completely random. Sometimes it takes the expenditure of huge amounts of energy, sometimes it just takes a slingshot around a star to get enough speed, and sometimes it just takes clicking your ruby slippers together three times! Secondly - and more worrisome - is the possibility of paradoxes, alternate timelines, and the like. The powers that be are already walking a fine line with many Trek fans obsessed with canon who are tracking Enterprise for the smallest detail that might conflict with what's already been established in the series (just why is it that the NX-01 isn't displayed in Picard's display of Enterprises? Sure, realistically, it's because nobody knew that there would be an NX-01 - but some people obsess over these things). When you then add in the posibility of creating pardoxes and alternate timelines, it's not too far fetched to wonder if the Enterprise series resolution will be some twisted take on the Dallas 'dream' scenario where Archer, Trip, and T'Pol screw things up so badly that the only solution is to muck with the timeline and erase the NX-01 from existance in the primary timeline (which, incidentally, would explain why the NX-01 isn't dipslayed in Picard's display...)!
Anyway...as far as the Vulcans go, yeah, I think a lot of people need to lighten up. But time travel? Let's just see where a linear timeline takes us for a while.
