I don't want to dismiss these out-of-hand, but they're really not a replacement for a modern application development framework.
Beyond functionality (of which these can and do provide considerably less), part of what makes a platform like Cocoa/UIKit so valuable -- it is used by every application on the device. The applications will interoperate both with each other and with the OS (background services/tasks, quicklook, spotlight, etc, etc, etc). The interaction model will already be familiar to the user, visual cues will be understood, the speed and inertia of animations (such as scrolling) will be expected. There is an enormous value to being able to leverage user expectation, and this is where too many choices falls down.