As i write this post on one. The macbook's speed aint a issue. The only issue for me is the screen size. If you plan to do real work on it, you may want to look at an second screen besides it, or an macbook pro 17inch.
My main workstation uses an bigger screen which (not apple) is more pleasant to work. If you really need that portability look at the Macbook pro, if you need real workpower maybe an imac is more your go?