Ok, here's the post I mentioned in my bleary-eyed state this morning before I retired for some well deserved shuteye...
iOS has had accessibility baked in since version 3.0 or so, which is simply activated by triple-clicking the home button, and after announcing "Voice Over On", it begins speaking. It also changes the gestures used on the screen, allowing a user to flick in various directions to read the screen, plus a few multi-touch gestures for such things as scrolling and switching home screens. In my experience, I find it fairly easy to use.
Android, on the other hand is a bit different. With Gingerbread and below, a sighted person would have to drill down through various settings menus (Accessibility and Voice Input and Output specifically) to enable accessibility. Usually it's 4 checkboxes in the accessibility settings (depends on what services you have installed, like Talkback, Soundback and Kickback, plus that all important Accessibility checkbox), then you have to pop in the Voice Input and Output settings and go into the Text-to-Speech settings and make sure the voice data for Pico is installed (usually is on new devices, with the exception of the T-Mobile G1 and most custom ROMs). It's an involved process, but once done, there's a fair bit of accessibility, but not the gestures like iOS.
Now for ICS... To activate the accessibility features on a new device (or custom ROM with all accessibility features baked in), you'd simply draw a rectangle starting from the upper left corner of the screen, clockwise around the edge of the screen, and back to your starting point. If done right, you hear a ding, and the TTS starts speaking, placing you in a tutorial to learn the gestures to control the touchscreen. Far simpler, don't you think? Since Quattrimus lacks all the accessibility features at the moment, I can't tell you how the experience is, but if you do a search via Google for Android 4.0 Accessibility, there's some YouTube videos that do show you a bit about how it works.
Ok, there's my kernel of knowledge regarding accessibility on Android and iOS... Feel free to fire your comments and questions my way, and I hope to work with y'all to make Quattrimus )and possibly other custom ROMs) more accessible out of the box.