Looking at some steam stats I'm seeing an average of between 20 and 40 people playing it at any one time, though chances are relatively few (if any) are playing internet-based multiplayer.
Interestingly, that's actually more than the number of people playing Valley2 by the same metrics.
FWIW AIW is between 30 and 70 at a time.
In all the above cases it's only steam and people not in offline-mode or otherwise playing it such that steam can't see it and so on, and this is during a sale on all of them.
