The usability problem wasn’t anything wrong with Flash intrinsically, it’s just that we couldn’t get it to feel enough like being in a browser. It was really, really hard to get the Back button working properly, and even things like letting people type in a query and launch it by pressing Enter (as apposed to clicking on a button) were a challenge.
This is pretty interesting. I'm starting to work on a new interface for the Packet Pickup Application and was thinking about implementing it in Flash rather than html or dhtml.