I'm a keyboard user, I don't like having to transition to my mouse to navigate through a form. It always stresses me out when I'm creating a new task or QOS in Team Explorer and I have to move the mouse to select the proper iteration.
Today I discovered Alt + Down Key. This will drop down the iteration combo box and then you can use your direction keys to expand and select nodes of the treeview. Right Key expands a node, Left Key collapses a node and Up/Down walk up and down the tree.
Turns out Alt + Down works to expand most combo boxes without selecting a value. The Up/Down keys will select a value in most combo boxes. You can also use Esc to collapses the combo box without changing the value. Enter obviously collapses the combo box and changes the value to the item that was selected in the list.
I know I'm a dork, but I'm so excited to save 2 seconds every time I create a new task.