XP32 vs Vista32vs Vista 64

[pupick]

Informal observation of disc access operations comparing Vista64 vs XP32 on
the same machine: nearly equal. I was quite surprised. Of course this is a
quad core uber machine with more ram than the 32 bit OS can access and may
be particular to this configuration.
Vista 32: time by your wall clock minute hand slower--only a slight
exaggeration.
Slooooowwww disc access has been, for me, the most disappointing aspect of
Vista 32 compared to XP--an utter waste of the horsepower in a modern
computer.
Win7: unusable due to instability and driver issues (this seems unusual for
a new Microsoft OS, no?): unfortunately no exaggeration. If Microsoft is
foisting a new driver model on peripheral vendors, as they did with Vista,
Win7/Vista SP3 will be another Microsoft clusterf**k.
Conclusion: it is worth running Vista 64 instead of XP32, as opposed to
Vista 32 for which the change from XP is not a rational choice, if you have
the right hardware and programs that can benefit from the extra RAM. The
right program is 32 bit Photoshop for which you will get, without having to
resort to command line switches, an extra GB of RAM in which the program can
run compared to a 32 bit OS.
The benefits of Photoshop CS4 64, which has total access to all that RAM,
are more difficult to quantify. I see no significant time differences,
meaning what a user notes in real time, performing the same operations on
the same images in CS4 32 or 64. Few Photoshop users will ever process
images that will run up against the RAM limits in a 32 bit OS, no matter
what they imagine, and the most common 32 bit Plug-ins do not run on CS4-64.