Pure gold. Mixing the minimalistic elements of The xx with the in-your-face lyricism of Biggie can't really fail. In fact, it works so well that Wait What made an entire mixtape of it (more on that here). Biggie's people weren't too appreciative of the mashup, asking him to cease and desist, but fortunately for us we've still got the Mp3s :-)
What would Biggie have thought about these mashups? Well, I can't really speak with any authority here, but I wouldn't be surprised if there was at least some inkling of appreciation / recognition. The xx managed to create a sound that was wholly new, though in no way surprising. Speaking of which, I presume that The xx themselves were pretty stoked to hear these types of mashups. Guesses are they wouldn't have anticipated it while recording!