Edit: lol, silly me, I didnt notice how old the origional post was.. woops, too many beers maybe
.. ah well you are probably a pro at UVs now
One small tip I guess to help speed things up is to lay out every island that is symmetrical vertically or I guess so all theyr centre points match up on a V line during construction, that way you just have to set the pivot point once.. very crappy and obvious tip, what can you do
.. nother crappy tip - if you just need to mirror certain islands, select them with island mode, then in either front / top viewport deselect the points including centre and texture editor should update, helps me alot.. If you are using component sync mode, select some points in a viewport first, then select island in texture editor, then deselect half in viewport..
I did just try out one emm, hack I guess for symmetrical uvs using clones outa curiosity (been messing around alot with clones recently hehe).. did a quick and nasty vid of it..http://www.youtube.com/watch?v=3UUOqoP2Vio
Isn't perfect and dunno If I will use it much myself, I guess might be handy sometimes. One problem is if you try to add edge loops etc to the origional non cloned half, the resulting uvs on the clone and merge can be a bit erratic / just give up alltogether. So I guess if you need to do any more modelling, would have to delete the clone and merged result (if you bother with one) first, then redo them after.. doh !. Though hmm, if you add edge loops to the merged mesh, then move around points on the base mesh's uvs, the new loops uvs will get nicely smoothed inbetween the moved uv points, same as they do when modelling.. could be handy maybe, hmm