64 bit
But they won't release a 64 bit version for Windows / Vista because, apparently, of the need to upgrade compliers.
So the next version of MS Office will be 64 bit and Open Office won't :(
Yes, I know it can run in 32 bit emulation mode, but why have a 64 bit processor, 64 bit O/S and 6Gb of ram to run 32 bit apps in a slower fashion ?