"...the 30D is best described as a refined 20D; shooting with the camera should remain largely unchanged, with the exception of the welcome increase in burst depth and more minor tweaks such as the addition of a 3 fps Low-Speed Continuous shooting mode and the ability to change the ISO while looking through the viewfinder. And most characteristics of the photos captured by the 30D should also match the 20D, since the 8.19 million image pixel CMOS sensor, multi-layer low-pass optical filter and DIGIC II processing circuitry are unchanged (though the 30D offers new image-related settings that will change the way in-camera JPEGs can look). The majority of the differences between the 20D and 30D appear when configuring the camera or reviewing photos on its rear LCD monitor. Here's a rundown of key changes..."I've been reading up on the 30D today, and Rob Galbraith has really delved deep into the press release from Canon and gleaned some important new details. Worth the read, and it got me more excited about the 30D!
This Canon site delves into the Picture Styles, which I found quite interesting.