A date attribute would be fantastic... For us, it would need to be an attribute, not a checkout step, because our products (cakes) have individualised delivery dates. A customer may order 2 cakes - one that needs to be delivered in 7 days, and another that needs to be delivered in 10 days.

Right now, I just use a simple text box attribute and ask customers to type in the date they require the cake.

This works... but a spiffy cal feature would be better!