Steam has less than 2,000 apps, and no-one would say that it feels empty.
The Mac app store launched with only 1,000 apps.
I don't think that the number of apps is particularly important as long as the quality stuff is there - can anyone who has used it comment?
Seriously I'm a fan of Windows Phone 7.5 and own a handset with lots of apps installed but it doesn't scale up to the desktop at all.
Not a single existing Windows user is going to bother with this crap - it'll end up going to way desktop gadgets went except you can't turn it off any more.
In Windows 8 you have to either check "Allow all trusted applications to install" in the Group Policy settings in Win Pro/Enterprise, or change a registry setting. This means users will have to go out of their way to install anything beyond what the App Store provides. Well, at least the option is still available.
Steam is an app store for games. Games purchases are impulse driven. When buying from Steam, you either go for a big title that you know you'll find on Steam or you go searching for something that triggers your interest.
On the other hand a large part of discovery on a regular app store is search-driven by actual needs of users that want to accomplish something very specific. Like, just the other day I searched for a way to view/manage my Picasa-stored photos on my iPad.
The number of apps is important for one because this means the app store doesn't solve many specific problems users are having and because Microsoft is known to have a big developer ecosystem since forever (building platforms is what they do best) - and so this lack of enthusiasm reflects badly on them and on Windows 8.
This only applies to WinRT apps. You can still install whatever desktop apps you want. So if you want to install Picasa, you can do it just like you would on Windows 7.
You must not have used Mountain Lion. By default it won't let you run unsigned apps. You can turn that off in System Preferences under Security & Privacy, but would casual users know how to do that?
>In Windows 8 you have to either check "Allow all trusted applications to install" in the Group Policy settings in Win Pro/Enterprise, or change a registry setting. This means users will have to go out of their way to install anything beyond what the App Store provides. Well, at least the option is still available.
Err what? To my understanding, what you said is exactly opposite, OS X has those restrictions and Windows 8 doesn't. Do you have a reference that Windows 8 restricts third party desktop apps by default?