According to Apple, the Mac app store shouldn’t be used for trial or demo versions of software. Instead, developers should use their own website to host such versions of a program. I can’t fathom what Apple’s motivation for this is — after all, demos don’t seem to hurt the iOS app store (I’d still prefer an XBLA-style model for trials on the iOS platforms, but that is neither here nor there).

That being said, I don’t think this is going to be as big of a deal as others might. The app store provides an alternative channel that, presumably, will have really high visibility. Home-grown advertising, by way of contrast, can be difficult, time-consuming, and expensive… especially for an indie developer, who would almost certainly rather be working on more interesting things. In the end, I don’t think it matters whether or not users are redirected outside of the store to grab a trial if they want it — I still think the store will result in more eyes on the developer’s application and website overall, and that’s a good thing.