That's difficult to explain....Should you buy it or not ???
If you wanna a living-room gaming system perhaps, then maybe...
Or maybe because your never purchased a gaming PC before. It will ease you into what's possible in PC gaming.
So, a tough question to answer. !!! You can easily build a PC for not much more and have better performance out of it.
Of course, it wouldn't be so compact and stylish as the Alienware Alpha.
I thing that review says it all: http://www.argyllfreepress.com/2015/08/17/alienware-alpha-review-gaming-console-pc/
Also worth to watch:
https://www.youtube.com/watch?v=-IYC6nnlkWw
https://www.youtube.com/watch?v=J5P3639BiDE
https://www.youtube.com/watch?v=yLhirRl8A1A