All I've found on turn out.

CCN says this: "Turnout was low."

The New Republic says this: "He canít blame the loss on turnout either: Turnout was greater on Tuesday than it was two years ago."

The NY Times gives numbers, but not percentages: "Turnout was not unusually low: More than 63,000 votes have been counted so far, up from around 47,037 in 2012." (What percentage of voters is that?? And does the 13,000 vote increase come from TPers??)

And finally ding ding ding from NBCWashington: "Despite the political ramifications of his loss, the election had a low turnout of approximately 12 percent in Commonwealth's left-leaning 7th District."

I wonder about the "left-leaning" tag, but if the 12% is a correct figure, I have to say that the result of the primary means absolutely nothing at all beyond what we all know, that activists control primaries. To be sure, that fact has obvious implications for the future of American democracy, but it also means that Cantor's loss ≠ a rising tide of TP importance.
MACTECH ubi dolor ibi digitus