Hi David,
Thanks for the feedback. You are right; this has been requested before (quite a lot). The feature has already been implemented and released in a beta, but there are bugs with it so it's not yet finished.
The next release -- 0.7.3 -- will definitely have this feature. In fact, its bugs are the only reason 0.7.3 hasn't yet been released.
It's implemented like so: on the Account-Settings dialog, there is a new checkbox for "Auto-populate password fields for this sites that match this URL".
Regards,
Eric