hah!  just found this thread today, glad it started so much discussion.
for me, this IS the summer that dubstep exploded, not just with MCs but dubstep in general.  the thing is, to break into large markets in the US you need names that are known.  I grew up in the midwest and trust me that the only things that make it big there are the ones that get played on MTV.  What this means is that people will hear that beat and be like "what the hell IS that?!" and then investigate and learn about this entire underground of music that's been brewing and evolving for time.  I'm not stating whether this is good or bad, I don't think ANYONE can make that judgment.  But I do think it will happen.
I for one like this vibe a lot as I was into hiphop for a long time before dubstep and am especially into the sounds of people like the Living Legends.  The instrumental choice is questionable sometimes and lots of people have mentioned that it's hard to hear the MCs over some of the raw wobbly basslines.  I definitely agree with this but also think that it gives a new feel to hiphop which it badly needs.
Time will tell...  
As to the Vex'd track it is a remix of scuba - twitch but I thought it was called satellites in the radio show, hence the naming.  Not sure on the actual name of any of the mixtape tunes so I changed it back to twitch.