Well I heard back from Kensington....

I asked if they were working on a driver for 64 bit mode in Snow Leopard

they responded:

Dear Damien:

Thank you for contacting Kensington Technical Support.

We understand that you would like to check the compatibility between MouseWorks software(version 3.0)and Mac OS X 10.6(Snow Leopard).

We regret to inform you that the MouseWorks software(version 3.0) is not compatible with Mac OS X (Snow Leopard) both 32 and 64 bit

We would like to inform you that we do not have any plans of updating the MouseWorks software. We apologize for any inconvenience this may have caused to you.

For any further assistance please feel free to reply back to this email or you may want to call us on our toll-free hotline number 1800-535-4242, Mon - Fri 07:30 am to 04:30 pm PST.

Regards,

Subin Augustine
Kensington Technical Support
Yeah .. I may want to call them and SMITE them over the phone

Funny thing is Mouseworks 3.0 works just fine in 32 bit mode as far as I can tell.