I frequently want to use Tab to indent my questions, for example to indent a snippet for code formatting. Currently, tab just moves me to the "Tags" input. I think most people would benefit more from being able to tag inside the question or answer box.
Here is how such a feature could be implemented: http://www.geekzilla.co.uk/viewA94BBC8A-8DC4-4F14-98F9-DEDFCF40DA07.htm
I realize this is a trade-off between easy switching between elements and editing, but personally I would benefit a lot from the faster editing this would enable.