I do a A LOT of app and window switching during my programmer work, and I (as any programmer) use keyboard to perform this switching fast.
At one point, I started to get pretty bad RSI to my left hand from all the CMD+TAB and CMD+` pressing, and I realized that these combinations were chosen very unfortunately, given the alternatives available.
So after some longer thought, I have remapped LEFT_CMD+TAB (Application switching) to LEFT_CMD+SPACE (for left and right thumb) and LEFT_CMD+` (Application Window switching) to LEFT_OPTION+SPACE (again both thumbs).
Furthermore, to unlearn the old habit, I have remppped LEFT_CMD+TAB to EXPOSE_ALL, and LEFT_CMD+` to DASHBOARD.
The price for this absolutely great improvement is that triggering the Spotlight (or Quicksilver, for those who saw the light), can only be triggered using the RIGHT_CMD+SPACE (not LEFT_CMD anymore), which is very easy to get used to.