Sooo...I guess the question I should ask is should I buy the Iphone 3GS as a less expensive start to the IOS ecosystem to accompany my Ipad mini?
I think that a way better and still cheap option would be the iPhone 4. In this way you can still upgrade to iOS 6 and, hopefully, 7 later this year. Plus, iCloud integration and other options that won't get with the 3GS.