i found a solution for this problem. i'm running windows 8 and idisplay would only mirror my screen. This is what i did:
go to screen resolution(right mouse button on desktop) and press detect. In my case 2 additional monitors popped up. turn one of these screens on and extend your main monitor. you only have to do this once!!
next start your teamviewer app on your tablet and connect to your laptop/pc. it should detect the monitor you just created so now you can switch to it. thats it. perhaps not the best solution but i couldn't think of something else and trust me i've tried.
about the performance... for me its just as good as idisplay or even better
and a bonus tip i want to share. install connectify on your laptop/pc and connect to your personal hotspot with your tablet. this wil speed things up quite a bit.