This has been floating around the net for a while. A lot of these are really cool, but now that I've started having to collect these things and refer back to them, the non standard ones have a tendency to get pretty annoying. In particular, the smaller cards (there seem to be a lot of people with the same size small cards...) have a tendency to get lost amongst all the standard sized cards. The other thing that can be really annoying is cards that you can't write on. Either they are dark on both sides, or too glossy, or whatever -- if you can't write down a note on the card, it becomes significantly less useful.
If you're going to do a creative business card, please at least stick to the standard size and shape. It would be annoying to have to carry around some of these odd shaped objects
Also, there's a fine line between "creative" and "gimicky". I'm looking at you, chocolate bar business card...