I have a pair of "Butler" Rhetts that I wear somewhat often. I love the shoes, but I do find they are somewhat hard to wear.
It's not so much that they're garish, but more that they're just out there enough that it's hard to make them a coherent part of an outfit or to find a situation where they're really appropriate. Their main use is for casual events and parties in the summer.
As an aside, not all of these are shell (in fact, I think most styles aren't), as I know there is a lot of confusion around this.