Thanks for the urls, I looked at them. Please look at demos of OneNote usage on a Tablet PC with a Wacom digitizer, the iPad bears no comparison. Firstly I can rest my hand on the tablet PC screen rather than having to hover over it. Mostly though I get responsive inking with pen nib resolution. The various iPad videos you reference show a noticable lag between stroking and the line being displayed, while resoultion seems to be at the finger rather than pen-nib level.
It sounds like the iPad suits your needs, It does not suit mine and does not match the level of stylus support I currently get from a tablet PC or slate.
My question about the suitability of an iPad in an Enterprise IT environment stands. I have used a tablet pc in a work environment and in government related work as a replacement for a paper notebook, I can't say I would be confident using an iPad in the same way.