You're talking about setting up limited user accounts correct? Have you ever run an XP box with a limited account as your primary account? I have two computers at home that I run in this configuration and to get all of the applications working has always been a chore, and beyond that to get the application preferences to actually take hold in some instances still does not work.
I've had to teach my wife how to run some apps as administrator since they refuse to work for a limited account and every reboot brings messages of applications that need to finish their install requiring an admin account which I can fix easily if I truly get annoyed enough, but sometimes I'm just lazy, especially since reboots are fairly infrequent (yes I said it, my XP boxes are really very stable).
I've never had these issues on my PowerBook despite running a non-admin account for the last 2 years. Don't try to tell me it's simple to run a limited user account on XP. It's not the most difficult thing I've ever done and I won't stop doing it, but I wouldn't tell anyone who doesn't know computers well to run in a limited account normally unless I really wanted a tech support headache.
I may be doing something wrong, but even according to some of my more XP savvy friends, running a limited account as your primary computer access on XP is not an easy task.