The internets are a rocking with posts about the iPhone's App Store unofficially hitting 100,000 apps, but while we wait for official word from Steve Jobs, the blogsphere is also debating the important of the sheer quantity of those apps, and whether that's more important that quality.
Scoble (and others, I think MacBreak Weekly covered this earlier) suggests that the huge number of apps makes for a greater chance each individual user will find that unique assortment that best fills their needs. In other words, while everyone has the same iPhone, they don't all have the same apps, and those apps essentially create a personalize experience -- a different iPhone -- for each user.
What's more, those must-have apps, and the money, effort, and time spent in acquiring, setting up, and becoming proficient in them, creates a cost that prohibits users switching to another platform. To go from iPhone to Android, in Scoble's example, means you lose Tweetie, Tap Tap Revenge, Photoshop.com, NASDAQ, etc. (Never mind if you've bought Navigon or other, high-priced content).
John Gruber, for his part, asks if the App Store is popular because the iPhone is great, or is the iPhone great because the App Store is popular.
The number of apps already in the store — and, even more so, the momentum with which new ones are being added — almost certainly guarantees the continuing popularity of the iPhone and iPod Touch for the next few years. But Windows is proof that popularity doesn’t guarantee market-leading quality.
But the iPhone isn't Windows. Neither popularity levels not quantity of software can be used to balance that particular equation.
Unlike the iPhone, Windows has never been a poster-child for great user experience (Windows 7 may alter that, but it's just going to market now). Fact of the matter is, the iPhone debuted in 2007 without an App Store at all, and sold for the entire first year (until the launch of the iPhone 3G and iPhone OS 2.0) without an App Store. It sold on the strength of its user experience.
It's that focus on usability that makes the iPhone great, and that in turn makes many of the apps great. Just like with the Mac, Apple has built in core technologies and development tools to handle a lot of the heavy lifting. So, while it still takes the very best developers to make the very best apps, even fair-to-middling developers can make apps that are surprisingly usable.
Those great apps, combined with a large quantity of usable if not inspired apps, is what makes the iPhone so compelling. The App Store itself is proof. Where Palm, Windows Mobile, Nokia, and RIM have had apps -- many thousands of them -- as well, it took Apple to create a single place, with a single home screen icon, to find and acquire them all. If it was just quantity, Apple would have had a hard time catching up to them.