Hi, JW.
I've been using the FZ10 all summer and getting pretty good results with it. From what I've read, they've improved the processor and of course, increased the megapixels from 4 to 5 in the FZ20. The lens will be the same.
I preferred my old CP 5000 to the FZ10 for macro work - the quality of the images is better to my eye. However, the image-stabilized 12x gives vastly better and more consistent results than the CP 5000 with a 3x extender lens. And, the controls on the FZ10 are so much easier to use than the CP 5000, particularly when switching to manual focusing. I've learned a whole lot more about digital photography in the past several months that I've had the FZ10.
You should look at the photo galleries posted on the Forum. I've noticed that a number of photographers here use the FZ10 and you'll get some idea from their work of what to expect from the FZ20, which should have even better results.
Some advice about the memory card. I have three 256mb cards and on a good birding week-end, I fill up one to two cards, which hold about 140 images each (4mp) as I use the high quality option. The 5mp image of the FZ20 will use even more space on the card, so you need to have more storage unless you use your images just for the web or small-size prints. I also strongly recommend that you buy a fast card(s), as regular ones significantly slow down your photography. I've bought SanDisk Ultra II cards and the Panasonic card. They are both speedy. Overall, I'd say that my Panasonic card has been a bit more reliable.
Also -- I've shot more than 3,000 images with this camera since late May and I haven't had a bit of trouble. It's extremely reliable. I'm about to buy a DSLR, but I'll hang on to the camera as a back-up and for walking-around.
I've learned a couple of other things about the FZ10 that have helped me, so I'd be happy to pass that info on if you decide to buy the FZ20. Best wishes in your decision-making.
Adios from New Mexico.
Ingrid