When I was choosing a laptop - I had a £700 budget, thinking, "I want to play games & do work". At the time I was stuck between a £700 Acer and a £700 MacBook. In hindsight, I wish I went for the MacBook and later saved for a gaming PC. The Acer had a good run, and could do gaming really well - medium-high on Crysis was pretty cool, but it didn't really have the stability I would have had with the MacBook, and really, playing games at a lower setting wouldn't have been so bad. Now, my laptop doesn't work at all.
Saying that, I mean, if you've got yourself a well built laptop, that won't betray you, then that's good, but I've noticed from hearing other people's woes, laptops for gaming don't always last. The M11x might be really reliable - I don't know what Alienware are like these days (aren't they owned by Dell, just as a note, at times I hear Dell horror stories), maybe somebody can vouch for their reliability? In my family, the only computers that have really lasted have either been a Mac or a Compaq....mind you this is being typed on an 8 year old Packard Bell, but our 9 year old Packard Bell is dead and this system like to BSOD on 3D games now...probably fixable, but I'm not going to bother.
If you're doing design, I can see the advantages of Mac - I know the argument, "you can do it on a Mac, you can do it on a PC", but strangely enough, people prefer design on a Mac than a PC, perhaps down to how the OS is laid out and the manner in which it performs...I can't say I've always had an interface, not even in Photoshop to respond at a crisp speed, it may take a couple of seconds sometimes, even on high-spec. Maybe it's how the the operating system manages memory that makes a Mac more desirable to those folks?
At least, that's my point of view. Personally, if I had the choice again, I would go for the Mac, but then you're not me.
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Also in hindsight, extended warranties are good things.

1-year isn't long enough for something to go wrong.