A question for whomever understands Vista's memory subsystem:
Is it possible that performance would increase for any particular workload
is swap is disabled?
A workload I have in mind is of a user who runs a program which uses a large
amount of memory to perform its own agressive caching (independent of
Windows's file cache) of its own data files, with the result that Windows
decides to swap out programs used by other users who are logged on to the
same computer, with the result that when other users activate their accounts
using Fast User Switching, performance for them is sluggish for a while
until their programs are swapped back in. If swap were disabled, then the
user with the program which performs agressive caching would not be able to
force other users' programs out of main memory, and therefore when those
users activate their accounts with FUS, their programs are still in memory,
so their performance is good.

It seems that this problem could be solved, even while still enabling swap,
if per-user memory quotas could be set, but I asked about this on Sept 5 in
microsoft.public.windows.vista.security in a message with subject
"Preventing simple local DOS attacks", but got no response.