In my case I couldn't notice any degradation. But I replaced the original HD with a 7200 rpm. The computer boots pretty fast (15 sec maybe), and battery life is ok. But maybe JT and VT differ in that respect

For a dual solution, vgaswitcheroo kinda worked, but you have to restart X to switch between cards. Ironhide proved more interesting for me since it could do the switching in realtime. Its ppa is here: https://launchpad.net/~mj-casalogic/+archive/ironhide/