Every time a major update comes out SWTOR forum gets overwhelmed with nerf rage posts, either "you nerfed my class (again)" or "why haven't you nerfed xy class yet".
Perhaps people would complain a little less if they had the opportunity to change their AC once after a "class balancing" patch/update (I'm not talking about those weekly patches, just those major ones like 1.2, 1.3, 1.4...).
Anyway I think that would give players a bit more options then raging, quitting their toons or not having fun playing them (and that's what it all should be about - fun).