Alienware while owned by dell as far as I know is still its own separate division so you should be just fine if you ever wanted another one. I have hardly heard anyone have anything bad to say about them
Alienware seem like LOOT for what they are. You are buying the name and a fancy case no?
Yes you are, but generally the components there made with are fairly high quality (capictors/boards etc) compared to the cheaper counterparts and brands. Also their support from my experiance is always much better.
Same reason why a lower end buisness series laptop (vostro) is generaly more than say an inspiron withthe same/better specs. You get better quality components and support.