Milind Alvares has some very interesting thoughts on the idea of multi-tasking as it relates to the iPad. The entire article is worth the read, but this conclusion sums things up well.
Instead of holding on to your old notions of how computers should work, take a look at what the new offers. The iPad is a half inch thick device, with multi-touch, forever connected to the internet, simplified, focussed, affordable, and most importantly, can be superbly productive. Sure it won’t be just as efficient and productive as your desktop or laptop, and that’s why they will continue to remain production machines, but given the iPad’s size and mobility, I think the lack of traditional multi-tasking is anything but bad design.
Smoking Apples: Understanding Multi-tasking on the iPad: What is it really?