Dell has owned Alienware for eight years but it has always been a totally autonomous subsidiary.
But as to Dell support, here's my story: In 2009, I bought a dell with dual video cards, which would never sync in SLI. Since the games ran OK, I just forgot about it. But about two years later I came across a thread that Dell had many returns on this particular system so just for the hell of it, I logged a ticket with them. Support replied and took control of my machine but was never able to resolve it. And then, Dell told me that since I had filed the ticket on the very last day of a two-year support agreement, they would replace the system. Again, it was a Dell machine, but they sent me the Alienware Aurora with dual GTX 350s. Now that's pretty damned good support.
BTW, the 350s in the Aurora also wouldn't sync; in googling that one I found others with the same problem which resulted from cramming those large GPUs over top one another such that the fan in the lower unit was sometimes impeded by a cable from the upper unit. And that was the problem with mine; moved the cable and the cards synced. However, now that one of the GPUs has died, I cannot run at highest resolution - single card overheats and occasionally locks up the machine. So that's my justification for upgrading. I can't upgrade to a 2GB card without replacing the mobo and I don't want to mess with that.