Hi Andrew,
It is interesting, but it has pros and cons. In any case it is a skin thing and would need to be implemented in the skin according to the needs of the skin and anyone could use it in their own skin if they choose to do so.
It does not require a new feature in mojoPortal.
For example you could drop the htc file into your skin folder and in the ie specific css files you could add entries that use it as needed to round corners or whatever else it helps with.
From the comments on that page it sounds like there are some performance issues with that kind of solution.
Best,
Joe