Doing some testing on a WP 3.5.1 clean install with only Jetpack and TwentyTwelve installed.
Enabled Carousel, Tiled Galleries and the mobile theme. Added a page with an image gallery.
On the iPhone, the images fill the screen width fine when in portrait mode. But when you go to landscape mode - to see larger images - the image actually fills a smaller portion of the screen and shrinks.
Sometimes it would show the caption in a vertical line instead of horizontal, sometimes the images would not be aligned, and they seem to get stuck and can't advance sometimes.
I can provide screenshots/video if you'd like.