Laptops were always and always will be netbooks and should never be used for any other reason. Ask anyone that actually knows about computers. If he says otherwise he doesn't know about computers.
it seems you are the one who doesn't know about computers, i use my 13" Unibody MacBook as my only computer and it works fine. 15" is the limit for laptops for me if you want to actually take it anywhere, though. loads of people use well-specced laptops as their primary machines. i could never get by with a netbook, losing 3 inches of screen space and a few pounds does not make it any more portable for me.