Garbz,
I agree. While the image quality if the iPhone and the iPad (assuming it's like all other Apple devices) is amazing, you can't calibrate it. If you can't calibrate it but you work on a calibrated PC to edit your images, chances are what you see on the device will not look the way you intended it to look. For a professional trying to showcase their work, this is a pretty ugly roadblock.
I also agree it should have ran a paired down version of OSX. I don't need another iPhone, I already have one. I certainly don't need one as big as a netbook to carry around with my already rather large 17" Macbook Pro. Since it can't replace the Macbook pro and is nothing more than a glorified iPod Touch, it would get left at home. Why on earth would I add the weight of the iPad to my computer bag when it offers me nothing I don't already have? I don't need a $500 portable House MD watching tool. I already have a tv in every room I spend time in and I again already have an iPhone.
Utterly pointless device that will be useful only to techno geeks that will force themselves to find something slightly useful to do with it and kids who want to play games and look cool to their friends. For people that use such devices to make a living, it's a major letdown.