I think it varies from region to region.

The dealer I spoke to sells just a couple of America / Speedmasters per year.

Sells mainly Bonnevilles in various forms (basic / T100 / Thruxton).
Tiger is another good seller for him too.
As is the Speed Triple.

I'd say the Bonny and Speed Triple are the biggest sellers - the 675 is SERIOUSLY gorgeous bike but I think it is too restricted in it's market.