I used to be a die hard laptop guy myself, until I realized that 99% of the time my laptop stays at my desk and I would be getting much better performance for the money from a desktop. The last laptop I owned was a Dell XPS m1730. It was a great machine, but I had to pay a pretty penny for it, and if you ever own a laptop you know that can get quickly outdated. Which is one reason I switched to a desktop.
I'll show you some other reasons why I switched to desktops.
You say you paid around 1200 - 1400 for I'm assuming similar spec to the link you posted with the exception of the 5870.
Looking over it, you'll notice that the processor is an under-powered 2GHz quad core processor, and the mobility radeon 5870 graphics card it uses does not perform anywhere near a desktop 5870, but it performs around the same level as a radeon 5750 - 5770 according to this site:
http://www.notebookcheck.net/ATI-Mobility-Radeon-HD-5870.23073.0.html. You can easily find an equivalent desktop for around 700 - 800.
Yes you also have to pay for the monitor, keyboard, and mouse for desktops, but unlike a laptop you don't have to throw them away when the computer is broken or obsolete. I will admit if you go to lan parties frequently it is convenient, but I doubt there are many people who can justify that.
Lastly, the one big thing I hate about laptops is when they get outdated you can't upgrade them, you have to throw the entire thing away and get a new one. With a desktop if my graphics card gets dated and I can't run any of the newer games smoothly I can just upgrade it to a new one.
I'm not trying to say that laptops are crap and desktops are the greatest. Laptops are great for people who need a computer on the go, but I just think that fpr most people a gaming laptop makes no sense. I think you'll get much more bang for the buck from a desktop.
Keep in mind I am just stating my own opinion and experience. I am definitely not trying to say that I know everything about computers, and I'm sure there are some people who can justify getting a gaming laptop, and I in no way want to put you down for your purchase.