The story isn't that simple. Many applications don't actually need all the memory they allocate all the time. Swapping doesn't have to slow down any application. A very good example is Poser 7, it now supports a way of swapping texture maps, having in memory only those portions actually needed at the time. It hasn't slowed down rendering and has allowed much more complex scenes to be rendered. In Carrara 6 you can minimize the program and watch how much memory is actually used (generally less than half a gig) but other memory has been allocated (and isn't in use at the moment, maybe not even needed in the rest of the rendering). Having more memory available (and in a 64 bit OS the limit is very high) leads to more memory being allocated and that leads to swapping. With care any application can be made to run without problems in a 32 bit environment.

That said a properly working 64 bit OS would improve many things. Currently the 64 bit Vista isn't stable enough yet to provide a good platform for software developers. So any hope that all 3D programs will be converted soon is idle hope, too many users will stick to a 32 bit OS for the time being and maintaining two systems is too difficult and expensive. Even MicroSoft itself doesn't believe in its own OS at the moment, the flagship Office package is only available in a 32 bit offering.