I like the desktop idea too. I just don't see how people develop on a laptop computer unless they have a separate, large monitor.
I have just purchased a wonderful HP laptop with an i7 quad core processor, 6 GB on memory, etc. running 64-bit Win 7. It is fast as ____ , and the display is wonderfully sharp--but that 16 x 9 aspect ratio is not ideal for much of the work I do. And it appears that all laptops now come with that type of display. I suppose they are aiming them entertainment uses. So I am still developing on my slower desktop with its large 4 x 3 ratio monitor. Perhaps I will replace it too in another six months or so.
And if you decide on a laptop, you need to compare apples to apples. Don't compare a cheap Windows laptop with a Macbook.