I would have gone for it... But already got my MacBook and I am quite happy with it. The 13in screen is really good, and I think 12in widescreen would be quite hard to work with. A 12in worked quite well in the regular 4:3 format allowing enough vertical space. A widescreen does not have enough vertical space with not much to work with.
I would have loved though, what somebody else already said, a 12" with minimum frame on the screen and keyboard, allowing to shave at least 1-2in from the width and depth of the macbook... Oh well, we'll see what will take place with time, who knows...
Umm..it's the height in *pixels* that matters not the height in inches!!!
If the 12" PB was 1024x768, and the 12" MBP is 1280x800, then the MBP would hactually have just as much vertical real estate!!!
800 > 768
P.S. I've also seen Sony's 11.1" widescreen and it's also quite readable at 1280x800.