I really like the way that this theme, the WordPress Twenty Eleven theme, looks on my mobile device, which happens to be an Android. One thing I noticed is that it can take a little while to load on my Android phone. It’s not slow, but I think it could be faster. That would take dropping some features that don’t get used, which would make it less easy to customize.
I started thinking about whether it would be worth it, and then it hit me. Mobile won’t be slow forever, yet it will always be small. Unless I’m particularly good at it, or I have a specific need to do it, it’s better to spend my time thinking about how to make good interfaces for small screen sizes than how to make them use fewer bytes.