I agree with Tuttle. At the moment, there is more potential than anything else. If you plan on keeping the system for the next 2-3 years, you will probably get a lot more out of it than you would today, and also more than you would with a 32 bit system.
64 bit systems to have some advantages today over 32. For example, when it comes do gaming, the 64 bit processor constantly gets better marks on benchmarks. When 64 bit games will be available, the 64 bit processor will have a big advantage over the 32 bit.