I only have two projects right now that have multiple WAP's. One is all Ruckus and the other is Ubiquiti Picostations...neither have controllers. Both clients are Iphone and iPad users and both seem to do just fine. 

The Ubiquiti job hangs on a little longer if I remember right, but that's because the AP's really aren't that far away, but the house structure seems to create terrible coverage. A normal house this size, I would have put a singel AP on the second floor and been done with it. 

What have you done for experimenting with different distances between AP's to see where the breakaway point is?