As of December 3rd, 2012, a WordPress.com blog stat page (https://wordpress.com/#!/my-stats/) now shows unique visitors in addition to total views.
The hint for each bar even does the views per visitor math (seems to average around 1.25 views per visitor on this blog, will update this when a longer period has passed).
The Your Unique Visitors from the Blog at WordPress.com explains some more details.
–jeroen
