Despite some opinions on the quality of Alienware systems, I own and am currently using an Alienware desktop. It is an Area 51 model and I have yet to see any performance problems with it after two years of constant use. All the appropriate software was installed by the manufacturer and it runs my most graphically intensive programs smoothly.
It is true, however, that Alienwares are a little overly-flashy. While LED keyboards and interior glow lights are sweet, they run up an electric bill pretty quick. If that is not on your list of concerns, then you need not worry.
I cannot really speak for Alienware laptops, but if you're looking into buying from them, you may as well get exactly what you want...upgrade the stock M11 to include more efficient parts - stronger processor, graphics card, etc. It costs more, but in the long run (oh, say 5 years down the road) when more graphically intensive programs are released, you'll be glad that you don't have to buy a new system / upgrade your laptop to meet their needs.
Also, don't buy Norton when they offer to install it before shipping. Norton blows and doesn't provide as good of protection as it advertises. Trojans can easily bypass it. Get Microsoft Security Essentials, SpyBot, and the like.