I have SPi's. I love the sticky gel toestraps and the relatively simple constrction (a good simple).
My gripes are:
1. Sticky ratchets
2. The design of the screw attachment point for the footbed is idiotic. The screw is fixed in position on the removable footbed and to attach it the the baseplate you have to blindly find the threaded receiving nut, which is mobile. In other words, you can't see it and you can't feel it. You just have to get lucky and hope the pieces line up and the threads find purchase. It's frustrating and deters me from wanting to adjust or remove my bindings.*
*this is the primary reason why I replaced my SPi's with K2 Formulas