Well I actually wrote that way back in 2002, and that 3yo daughter is now 15. How funny that Mothering is still finding me with responses.
I'm guessing Elsa's post below is spam -- otherwise why would she have found this ancient thread and post for the first time with an unidentifiable link (don't click on it!).
But since I'm here, I'll give an update. interestingly, it turned out that the reason she was late to use the potty had an explanation. Turns out she has Asperger's Syndrome and the late potty-training was related to that. Our lifestyle (unschooling) kept other signs of Asperger's from being so easily noticeable for a long time. by the time she was 10, we were seeing more and more that wasn't matching up (i.e. difficulty interacting with peers, continuing to throw tantrums past the age of tantrums, and more.
Well, as I said, it turns out she has asperger's, and this was one of the earlier signs. I don't mean this is the case with every child who is taking a while, but it is worth staying aware of how your daughter is managing other developmental milestones and mentioning what's goign on to your doctor.