I too own the U20 (silver). I got a 64MB memory stick for the camera which I find is good enough, usually the batteries don't last long enough to fill it up (160+ images).
Personally, I've found that the camera works well for outdoor and/or brightly-lit subjects. Indoors, you'll need to use the flash or you'll end up with noisy pictures. The quality of the JPEG compression is a little bit on the low side, too.
I really like its size and quick startup time, allowing me to carry it just about anywhere and take on-the-spot pictures.
Have fun with your new digicam!

atwl