This was released some time ago, I think I have it for more than one month. For the end user I guess there are not many changes, excluding and the bugs and security issues that were solved.
I'm not sure why Microsoft released this at all. Its changes are so minor, they could have just done separate updates for them instead of a new SP
They released SP3 so you can have all the updates offline when installing Windows. Do you like to download 40 updates everytime you install XP SP2?