I think the biggest thing that Marco and Rafe are missing in predicting the success of the Mac App Store is the (current) pointlessly complicated installation process on a Mac. Have you ever taught someone how to install apps on a new Mac? Or remember what it was like the first time?
Since most people come from Windows, they're used to this process:
- Download an .exe/.msi installer (or if it is a zip, unzip to get your installer)
- Run the installer, run the app
On a Mac, the process usually goes like this:
- Download a zip file
- Drag application to Applications directory
- Delete downloaded zip and extracted contents, then run application
- Download .dmg file
- double click it to "mount"
- Follow whatever instructions are given, usually have to open a new finder window to drag application into Applications
- unmount disk image after installation is complete, run app
- Download zip/dmg (unzip if needed)
- Run .pkg file installer
- Give your admin password, complete install
- remove/unmount downloaded files, run app
As easy as the Mac is to use, I've never understood why the installation process is so varied and tedious (I understand there are obvious security issues that complicate the process, it still sucks for the user that wants everything to be easy). I've had to walk friends and family through this several times and it takes half a dozen tries before they start to get it right on their own (Try explaining to someone new to computers why you must "unmount the disk image" or what that even means conceptually). People often get tripped up when nothing happens after they download a .dmg file (Why do I have to mount it first to use it, why doesn't it just work?).
My biggest Mac app installation pet peeve is when a mounted disk image runs in its own Finder window without the helpful sidebar, so I can't simply grab the application and drag to the Applications folder on the sidebar, but I have to open a new Finder window because the features were disabled by the application writer.
Make no mistake, every Apple store in America is selling new Macs like hotcakes, to many people that have never owned one before. I bet a large percentage of new owners just stick with the shipping apps of iTunes, Safari, Mail, iLife, etc and don't install apps without help from the Genius Bar or friends. It seems crazy to someone like me that has used a computer daily for 20 years, but you can probably do a lot of things with a stock Mac without installing any additional apps.
A Mac App Store is going to be a boon for developers and Mac owners because it'll finally get rid of the clunky installation process and make the whole thing as easy to use as installing an app on an iPhone. Click into the App Store. Click an App, Click Buy, Run the App.
Marco (and Rafe) are right that this will be huge, I just think everyone is underestimating the potential upside of improving the usability of Macs in a big way that has been overlooked for far too long.