i've had an FZ20 since November of '04. when the '30 was announced, i looked at the features, considered the relative value of the new bits and whistles, and decided it wasn't worth my money and the hassle involved to "upgrade". from what i can tell, the '30 does not give you any better pictures, just bigger ones. it is an incremental improvement on the FZ20, and even then only in terms of some handling features and tricksy capabilities. if i'm going to spend money upgrading my equipment, it's going to be for something that will really BE an upgrade, and will give me a noticeable, dramatic improvement over what i can get from my FZ20. those who follow my posts know i've recently ordered a Canon 30D for just that reason.
my 2 cents? keep the FZ20, and when you do decide to move up, really move up. don't waste money on a half-step that you'll want to upgrade again in 6 months or a year. the FZ20 will provide image quality just as good as the '30, and if you aren't trying tomake mural-sized prints, you'll likely never see the difference, so unless the handling features are a real sticking point for you, save the money and start a cookie-jar fund to buy something that will be a real upgrade for you.