I did not particularly care for it.
It's almost indiscernible from the majority of dubstep. The background sound (by that I mean the sound behind the wubs) does not fit the Portal theme well. It doesn't sound much like anything from Portal. The overall pattern of the wubs doesn't give that Portal feel well and actually sounds like something from an RPG game except in a few places (like 1:39 to 1:48) where it is slightly reminiscent of Portal.
The redeeming components were the inclusion of voices from the characters and the gameplay screenshots. Including the "wubs" as text in the video was also a good decision.
Overall, it doesn't stand out well amongst the other dubstep. A genre which itself is plagued by being largely made up of sub-par songs.
That being said, it's good to see someone putting a bit of effort into Portal-themed content. Portal 2 is an amazing game which completely beats Portal in terms of quality and gameplay, and Portal was a great game to begin with.