Well, for some time ago was forced to downgrade the old dual-p2-333 from win2k to NT4, resulting in VLAR taking 1-2 hours less. Then v3.08 later was released, cut yet again some time off the crunching, so if remembers correctly v3.08 averaged 17h on VLAR while 18h20m on "normal" wu under v3.03...
On other angle-ranges didn't detect any noticeable differences between NT4 & win2k...