The new gestures in iOS 4.3 are neither obvious nor discoverable. Will anybody instinctively know that getting back to the home screen requires a pinch gesture with five fingers? (Using more than one finger also precludes one hand use and is awkward on an iPhone or iPod touch.) You can currently comfortably use iOS without ever putting more than one finger on the screen. Zooming might be less precise but double tapping works perfectly fine (edit and correction: you need to double tap with two fingers to zoom out in Maps so this is not entirely true). A departure from that principle would be weird.
These gestures are nice shortcuts but, I think, not much more.
I might be less skeptical if there was any credible evidence that Apple plans to steal from Palm and Blackberry and will extend the touch surface onto the bezel. That would allow for much more obvious and intuitive one finger gestures.
That said, Apple does weird stuff from time to time. The iPod shuffle had no buttons for a year. (At least Apple is also willing to correct such mistakes. The current iPod shuffle regained buttons.)