The F2.8 throughout the zoom range is the main reason why I bought the FZ series in the first place. So far been quite happy with the 1 day I've had FZ20.
Having said that I had a Nikon E5000 and it took some great pictures. Very flash happy tho'. My current Olympus 5060 seems to fire the flash off a lot as well, but battery life on this camera is excellent.
Hope they have addressed the shutter lag, slow data upload and short battery life in this new Nikon.
read imaging-resource's review and you might change your mind keeping your fz20.