My first install of SP2 went horribly wrong (see other posts in the Helproom) when I downloaded it from the Microsoft website for my desktop. It seems to be sorted now after many re-boots and many CHKDSK operations on boot up. In hindsight this may have had more to do with the fact that 2 days earlier I had expanded my Hard Drive using Disk Director 10 (via the XP partition.
Installing SP2 on the laptop that I share with my wife was therefore fraught with the danger that I might screw the machine up and thus incur her wrath, but I am pleased to say that the install went well and so far no problems have been encountered.
I have yet to see any advantage of having SP2 but maybe they will show up over time. I have noticed that on both the PCs that I have installed this Service Pack on the boot times ie the time from switching on to getting a full desktop is considerably longer, Sidebar is particularly slow to come up.