FX's head of PR John Solberg tweeted the news that thepremiere last night was more than 50% better in total viewers and 41% better with adults 18-49 than last season's averages. While no specific numbers were provided yet, I'd guess that is around a 0.7 adults 18-49.
The season one finale last March averaged a 0.4 with adults 18-49 and 760,000 viewers. You can see all of Archer's season 1 ratings here.
Update: 1.5 million viewers and a 0.87 with adults 18-49, down from the S1 premiere, but up from the S1 finale.