I really don't get this argument. What was with difficult with using Google and downloading an image file and dragging it to the Applications folder? Right. Nothing.
The only thing that the AppStore makes simple is spending money on downloads. I find it extremely cumbersome to find a good(!) app for a specific purpose in this mess of a database - ahem, store - and I cannot even try it before a purchase.
Downloading is easier. People spends money for apps whether they go to the Dev website or to the App Store.
The App Store however makes it easy to find apps. Maybe is easier for you to look for an app through the web, and then check whether is a .dmg or .exe file, some people are not good at this.
About the demo, is better this way. No shareware, trial or beta to flood the store. The dev can write in the description of the app to fo to their website to try it - is their fault if don't do that.
For example PopCap has Bejewled 3 on the App Store but they didn't say anything about the trial they have right in the home page of their website.