Everybody seems to be writing reviews at the moment, so I thought I would include this one from jazz hooves, as 1 person’s opinion of the Wersi Abacus.
http://www.jazzhooves.com/page12/page38/page39/page39.html

I have also included the link to my own review for another opinion.
http://www.synthzone.com/ubbs/Forum37/HTML/018501.html

The first one also mentions the OAA, mine does not as I don’t have it.

Regards

Bill