My experience with installing XP SP3 was mostly good. I rebooted and furrowed my brow during the lengthy shutdown; the wait for the system to boot up didn't do much for my system. The first screen that appeared advised me that Microsoft didn't like my Automatic Updates settings. Microsoft wants me to let it run the updates automatically. Tough luck, Bill -- I want to decide when to install any updates. (See Quitting Time Is Best for XP's Automatic Updates.)

SP3 doesn't like my Updates settings.
Once my system settled down, the Quick Launch tray appeared, and the System tray was fully populated, I started trying applications. Keytweak, a handy keyboard remapping tool, was the only program that wouldn't run. (See Quick Keyboard Tricks, a Neat Keyboard, and a Notebook Docking Station for a KeyTweak review.)

One of SP3's victims: KeyTweak
SP3 Speeds Up My PC
As I launched and tested applications, I noticed that every program loaded faster. My usual cast of characters -- Eudora, Explorer Plus, Maxthon, Ad Muncher, Kaspersky, WinPatrol, and others -- all suddenly appeared more quickly on screen, ready to go to work. Office 2003 apps --Word, Excel, and Outlook -- were especially quick to load. Sure, I agree, it could be a perception thing (I haven't changed my blood pressure meds), but I don't think so.
And so far, I haven't heard from readers experiencing any major disasters.
Of course, I'm curious about your experience (my address is below). Any big changes after SP3?
Service Pack of Troubles?
If you do have problems with the upgrade, you can receive help from Microsoft for any update issue free of charge at the Microsoft Windows XP Service Pack 3 Help and Support site. The site includes E-mail Support (24 hour response time), chat support (11 minute response time), or by phone at 866/234-6020 (varying response time).

Help for SP3 installations.
Talkback
What's your take? Are you going to grab SP3 yourself or let Window Update do the job? Or maybe ignore the whole thing and buy a Mac? You can use Comments below or if you'd prefer, fire an e-mail right into my inbox.
Installed SP 3 this evening in about 30 minutes flat including downloads (over 6 Mb connection). Used Windows Update after the dowload pack refused to install (that confusing free/retail, either/or thing).
Zero difficulties, except I had ActiveX disabled in Internet Explorer on principle, and WU uses it to inspect and download updates. If anyone reports a blank page when trying to connect, that's probably the reason.
Three little Windows saying installation of one file failed disappeared with a click on Retry.
Results: everything does seem a bit faster. I'd say roughly 10-20% on some things. I don't use Microsoft suites like Office, but OpenOffice seems a bit quicker. Firefox opens faster, and the ancillary stuff like Memorizer (my pet clipboard extender) and WordWeb snap open. Some of that's likely due to cleaned up files. Installing a Service Pack is more or less a clean install of WIndows.
Now, if WinPartol will just stop telling me about all those changes...