One answer is what VW customers do with 64-bits.  Travis & Martin can give more up-to-date answer on this but IIRC a number of VM customers had images that were pushing the 4Gb limit.  One was Quallaby.  They did a network monitoring app that had huge numbers of large integers in a graph representing the state of the network.  EZBoard wanted 64-bit images because their message-board architecture was too monolithic.  GemStone had/have customers hitting 32-bit limits on numbers of objects.  So I'd sum up as large enterprise apps.  Travis, Martin, what's the current demand like?