Re: Actually, there is a middle category, probably more important in the short run (than 64 bit apps able to take advantage of 4GB of memory). It is regular 32 bit applications that will go from 2 GB support to 4 GB support.
This is not as beneficial as you think. Windows requires 2GB of its own whether or not you are running in 32-bit or 64-bit mode. So you will not be able to run your 32-bit apps with 4GB of memory, unless you have 6GB of memory installed. And how much does 6GB of memory from HP cost these days?
Now multiply this by the number of total blade systems in a given rack.
I can see certain select servers needing a big memory footprint, but I have a feeling that the transition to large memory blades is going to take a while.