At first I thought that Ubuntu was much slower than windows on
booting up but impressions can be deceiving. Windows does a good
job of showing you your desktop as fast as it can but you can't
actually use it for a fair bit longer, and launching firefox asap
incurs a huge delay, evidently because certain services are still
being started up in the background.
This XP install is fairly vanilla. No AV software or anything
expensive put into auto-startup. Most of the stuff Sony threw in
was removed or disabled.
Ubuntu is up and multi-user earlier than XP, at about the 25
second mark after grub kicks it off, but takes longer to give you
a fully functional desktop. Once the desktop appears, however,
the machine is pretty much devoted to your needs so it is able to
start firefox in just 5 seconds or so.
In both XP and Ubuntu, the wifi network is up and available
before you are able to use it.