In my use case, every time I've tried to replace my MBP with an iPad, the lack of pointer support always rears its head. When using it in landscape mode on a desk, its a total pain to try and use Safari when you have to keep touching the screen. I suspect that's been the same for quite a few people who have considered switching.
Yup, the new mouse and trackpad support adds a lot of comfort when working from a desk in a lot of cases.