Hi Bill,
I'm not a wedding shooter (don't have the nerves for it -- would prefer bomb disposal I think!) - but I would have thought that in terms of wedding exposure - shooting RAW - that there would be more than enough lattitude to under-expose a dress (thus ensuring the retention of highlight detail) by a minimum of 1 stop, if not 1.5, without penalty?
Personally, I've learned that even with landscapes it's something that's preferable (assuming the wasted dynamic range isn't needed at the shadow end) to retain good cloud textures. I haven't done any formal test, but I suspect that the sensor is getting somewhat non-linear around the very top end of the range, resulting in a distinct lack of contrast within the highlights (or perhaps it's a display issue - all I know is that they're easier to work woth - and I get better results - by under-exposing a little.