I've recently upgraded from utopic to vivid (14.10 to 15.04) and whilst there are a few small issues the main thing is that my touchpad (logitech t650) is not working as it was, specifically I can no longer use a 3 fingered swipe left or right to move backwards or forwards in a browser, or nautilus when looking through files, other than that the touchpad works fine, although it does need tweaking as it isn't as smooth to use as it was in utopic.
I have tried numerous things and had no luck, I've already upgraded the firmware by the way, the annoying thing is I can plug it into my wifes system (running 14.04) and it works perfectly with no configuration (including 3 fingered gestures), this was also the case in utopic but not for vivid, as far as I can tell it no longer supports 3 fingered gestures in vivid, I've tried programs like easytouch, touchegg and some others but all of them don't see the 3 fingered gestures, I also used geisview to see what the touchpad is capable of, and according to that it's not capable of 3 fingered gestures.
In all honesty I'm at a bit of a loss as to what it might be, so any ideas would be appreciated.
Since writing this I have been doing some experimenting, and I have found at least for me a way to get 3 fingered swiping, I basically use it for browser navigation, but with more tweaking it might be possible to get a lot more of the touchpads functions working.
After searching I came across this - multitouch gestures it's taken a bit of messing about with, but that's more my lack of knowledge than anything else, I did have some issues when running some of the commands (specifically the make commands) turns out this might be down to glibc, but I found that using this source solved the make issues clone from here if having make issues
I still have some issues with the touchpad, but this seems to be a step in the right direction, hope it helps.