There is no question that every Windows XP user should acquire and install this update once it becomes available. Windows XP Home users will still be lacking in a number of very key security features that exist in Windows XP Professional (see 5 Steps To Secure Windows XP Home, but with SP2 it will be significantly more secure than without it. Not only will applying SP2 add all of this new security functionality, but it will apply all of the patches for the operating system up through the date they publish the Service Pack so the system will be protected against all of the known vulnerabilities through that time.
One of the biggest issues facing users will be acquiring the update. I have heard reports that it is in the 200Mb range, however the RC1 version that I downloaded was a 475Mb download which would take approximately 20 to 45 hours to download on a standard dial-up connection. While broadband use is growing rapidly, there are still a vast majority of users- the very users who need the updated security the most- who are using slow dial-up connections to access the Internet.
Perhaps Microsoft will offer to ship the CD for free to registered users by request. I have contended that Microsoft should partner with distribution outlets like Blockbuster Video or Best Buy or Target or something to offer Service Packs and other large updates on free CD's for the taking the same way the ubiquitous America Online CD's are pushed. If neither of those things occur, you might consider downloading it at work if you have highspeed access and won't be violating the AUP (acceptable use policy) of your employer, or find a friend with broadband access and a CD burner to help you get the patch.