The transition from 32 to 64bit is unavoidable as time progresses. The differences here over going from 16 to 32bit a decade ago is that the market place for softwares as far as desktops are concerned is still 32bit while MS provides a degree of backward capability with each new version including the 64bit editions.
Performance wise you can't expect to see any immediate gains while the 64bit editions take into account the increased capacities for memory seen on the newer boards. Yet there are still problems seen when simply going to install a 64bit edition with over 2gb of memory installed with certain hardware configurations.
Many rushed at a 64bit edition expecting to see some large performance gain since more memory is available as ram with 64bit over 32bit due to limitations of mapping out memory addresses over a certain amount to hardwares making them unavailable for games, apps, etc. in a 32bit edition.