Hmm...I just did a tour with 14 panos and did´nt notice any slow down?! Even on the very first iPod touch, which is the slowest iDevice from Apple, the performance is (almost) normal. Are you using the thumbnail-gallery? If yes, I would assume that´s the reason.
We are designing a new interface for our virtual tours and are encountering the same problem with the thumbnail gallery, slowing down is happening in several devices, crashes also, mostly iphones. Any ideas on how to optimize?