I am really loving Aquaria's demo, and I would have bought the game already except that Ambrosia is porting it to the Mac - I'm running Aquaria under Boot Camp currently, but it would be way awesome under OS X.
Would you consider allowing your users to crossgrade to the Mac version (maybe for a nominal $5 fee or something - Ambrosia ought to get paid too of course)? I'd be happy to pay a little extra, but I'm probably not going to buy it twice.