Good for Apple, but they are way over-valued if you ask me.
I really don't think so. Look at the markets they're thriving/dominating in:
- PCs (not dominating, but one of the largest PC makers, and with high margins)
- Smartphone devices
- Tablets
- Music sales (iTunes)
- Video sales (iTunes)
- Software sales (iOS and Mac App Stores)
- Books (iBookstore)
- Music players (ok, probably a shrinking market now)
They have their fingers in a lot of pies, and that makes them very resilient to changes/fluctuations in any one market. They're also strongest in new emerging segments (tablets, full-sized lightweight notebooks like the Air).
In fact, I think the iPad is going to get much bigger for Apple. For me, it's thriving even without a killer app. It has lots of apps, but no one app that you'd say "I'm buying an iPad just for that". Several of my friends have bought one and said the same thing as me: "It's cool and I love it, but I'm still trying to justify buying it".