Just a little info about laptop speed-todays new machines, LT's especially, are as quick or quicker, equal too, any desktop-the machines speed is dependent on processor config, software installed & setup. Batteries are being designed to last longer with the new processors being more efficient its an all-win situation. Power supplies do fail in desk-tops/all-in-ones, both types do fail for different reasons. Most LT's today are not user friendly in that they are not designed to be opened by the home user, now a warranty issue if service is other than certified tecks. The new laptops are basically 'what u buy is what u have', in that they are a non-upgradable device, they can be worked but usually not advised on the 'package' machines. Dependability is about the same on all pc's today. I always tell prospective buyers to buy as much processor as u can afford & buy SSD's for the hard drive or C drive as referred to-less moving parts to fail, lower power consumption, lower weight. They do seem to be getting better as the technology goes-stevie...As a side note: I don't think a laptop should replace desktops, no matter how awesome they are. It can be the POWER MAC 5000 that can do everything and blend for all I care.
Little known tidbit: laptop batteries eventually run out and have to be replaced. Also, price-to-price, desktops are a lot faster than laptops, PC or MAC