I also installed SP3 when it came out on my workstation as a test, and I have not seen one problem. I have read a bunch of posts on SP3, and it does seem secure....
There is only one thing I really don't like about SP3, and that is the upgrade to Windows Update it automatically performs. This is from the About page on Windows Update:
"Windows Update Privacy Statement
Windows Update is committed to protecting your privacy. To provide you with the appropriate list of updates, Windows Update must collect a certain amount of configuration information from your computer. This information includes:
Operating-system version number and Product Identification number
Internet Explorer version number
Version numbers of other software
Plug and Play ID numbers of hardware devices
The Product Identification number is collected to confirm that you are running a validly licensed copy of Windows. A validly licensed copy of Windows ensures that you will receive on-going updates from Windows Update. Windows Update does not collect your name, address, e-mail address, or any other form of personally identifiable information. The configuration information collected is used only for the period of time that you are visiting the site, andis not saved.
To provide you with the best possible service, Windows Update also tracks and records how many unique machines visit its site and whether the download and installation of specific updates succeeded or failed. In order to do this, Windows generates a Globally Unique Identifier (GUID) that is stored on your computer to uniquely identify it. Windows Update records the GUID of the computer that attempted the download, the ID of the item that you attempted to download and install, and information about your operating system version and Internet Explorer version."
