Check this out:
I will definitely consider this, once I get a 5DmkII. Have you ever noticed that your pics seem just an inch or two off focus from where you “thought” you had focused. For the most part, an inch or two isn’t a big deal, but it can make or break certain shots.
This won’t solve any user focusing issues (in other words, you still need to focus properly), but it will fix any minute discrepancy in the camera’s set-up. Now, I just need to get a 5DmkII. One thing at a time…