Oh Dear!
Tried my 24-105 and 17-40 on a 550D, standing in for as yet unavailable 600D. The 25-105 does not balance at all well on such a small camera and the lens dominates. In fact for (not) inconspicuous street shooting, all people will see is the lens, so advanatge over 5D2, zero.
So back to square 1 - it will have to be GH2/14-140 and 24-105 to ebay to offfset cost. The 24TSE is going to clean me out so I'm going to have to use my LX3 when need wider than 28 (travelling).
BTW, the ergonomics of the XXD Canon's are sufficiently different to the 5D2that, if you are familiar with Panasonic menus through the LX3, I think the learning curve may actually be less.