Windows Security Center, Windows Firewall, Automatic Updates, IE enhancements...
New in SP-3:
A package that contains all previously released security patches, performance enhancements, and various bug fixes for earlier Windows XP service pack releases,
as well as several new functionalities; Release Notes - Last Updated: 05.06.08 (SP3 Official Release)
Upgrade Meter:4
New in SP-2: Across-the-board security enhancements and infrastructure, Windows Security Center with Automatic Updates technology, enhanced networking features (new Windows Firewall - replaces ICF, Windows peer-to-peer networking, wireless provisioning services, and updates to IPv6), new IE information bar and add-on manager, increased manageability and control, Outlook Express attachment manager and privacy update, BlueTooth support, "enhanced user experience"; Complete List of Features; Release Notes Upgrade Meter:5
New in SP-1a: Does not include or install the Microsoft VM, which provides support for running Java programs (per Microsoft/Sun court injunction); no other changes or fixes. To be followed shortly by SP-1b, which will feature Sun's Java; Release Notes Upgrade Meter:1
New in SP-1: Several hundred bug fixes for the following areas: setup, application compatibility, operating system reliability, and security; Release Notes Upgrade Meter:2
Pros: Improved security for Windows XP, built-in Firewall, better control over pop-ups and browser add-ons, Windows peer-to-peer networking feature, enhanced IE browser, wireless networking enhancements, free upgrade
Cons: New security measures and built-in Firewall can take some time to get used to (especially for web browsing and file downloading), some security enhancements are counterintuitive, less-than-perfect integration with – and doesn't eliminate the need for – third-party apps
