I have a webOS phone (in fact i have four - two Pre's (inc a Pre Plus) a Pre 2 and a Palm Pixi Plus) all of which I've devved for - free and commercial software. I also have a HP TouchPad that uses webOS.
The OS is absolutely wonderful and fresh, with great gesture controls and very easy to code for - there's no certification or Xcode shit like on iOS and there are no fees to create or release software (HP do take a 30% cut of any sales though). The only things that actually let the OS down were the hardware running it (performance-wise) and HP themselves. Stupid feckers.
It would be great to see Pandora running webOS in the future, although a capacitive touchscreen would be required for certain functions.