And you can even upgrade processor, RAM, HD easily. I've read it's even possible to change the GFX card, but who's going to manufacture and sell the modules .... ?
Dell, Alienware (and I believe Sager) tried the whole "upgradeable mobile graphics card" marketting thing a few years ago.
What ends up happening is that the OEMs are the only ones you can buy the parts from, and they'll charge you an arm and a leg for it. Why not, right? They've got a monopoly on the parts for their own line-ups (heatpipes, etc, may vary from model to model) and they know enthusiasts will pay through the nose for it. Especially if they're worried about voiding the 3-4 year warranties they might have sprung for back in the day.
Also, with some of the upgrade paths to my current laptops, the newer cards needed different batteries and PSUs, making the upgrade path even more expensive.
I'm burnt out on "mobile performance" these days. I prefer to have a nice, cost-efficient home rig that's easy to customize and upgrade, and aim for value in the mobile segment. My next laptop will have respectible graphics, but I'll stay away from the bleeding edge (in terms of price) and keep it reasonable this go-round.
That all being said...these Gateway laptops have been getting great reviews. My only beef is the plastic bodies (I prefer metal), but at these prices for those parts, I don't see how they can be beat!