This is in line (if at the low-end) of the forecasts, equaling about 30% of turnout. Democratic candidates got a little more than half the votes -- about 650,000 combined. Here's an examination by the MJS' Craig Gilbert of the past primaries.
Here's the problem for Democrats. It is possible that Republicans did not come out to vote in full force -- it may not have been obvious to voters that Walker was on the ballot at all. The Democrats can't hope that the same holds true their voters.
Some history here. Gray Davis' recall saw a much higher voter turnout than in the previous election (2002). We should definitely that the recall will see something like the 2.1 million voters who cast their ballots in the 2010 gubernatorial. Perhaps Democratic primary voters didn't care, or perhaps their vote is simply and "anyone but Walker" one. Whatever the reason, the Democrats probably have to step up their turnout game to win in June.