I use the Panasonic LTZ10 and am very satisfied with it.
I find there is no light loss and no degradation of images with the FZ10.
It should be the same for the FZ20.
It also comes with mounting bracket which would take the load stress off the camera attachment ring and position the setup for proper balance on a tripod/monopod.
What I hate about it is it seems to take forever to screw onto the camera and changing between tele and wide-angle becomes tedious.
Also there are no threads to mount closeup, UV, CP filters etc or hood.
If anyone has any suggestions what I can get to fit close-up filter or hood on, I would be really grateful.
Don't forget you first need a DSLR to use their lense.
And what do you think a "premium" lens with IS, 35-420mm & F2.8 plus 1.4X teleconverter through the range would cost? Also what about the weight?
I do own a SLR but looking at this, I guess such a lens would be at least equivalent to a dozen FZ20s (and more than I can afford): http://www.kenrockwell.com/nikon/40028afi.htm
Therefore, I will still be hanging on to MY FZ10 AND LTZ10 come time to upgrade to a Minolta 7D.