I NEVER use ISO 400 - if anything I never go above 200 - 50 is my norm!!!
The image stabilization is so good you really don't need to go higher - you can handhold no probs at 1/60th on full zoom = 420mm!!!
Shutter lag will never compete with an SLR but it comes pretty close. If you do nothing but sports photography it may not be quite quick enough but for most people it will be ample - really is better than the other budget cameras out there.
I really do find it incredible value for money. A mate of mine has a top of the range Nikon digital SLR and after trying my camera he now uses the Panasonic 90% of the time.
I WAS going to suggest getting the new FZ30 - same lens but 8mp BUT then I noticed it is NOT quite the same lens - apeture now varies a bit - WHY???