1. Google's Play Store and Palm/HP apps were easier to search and easier to install (no need for iTunes!). I could even browse the sites and select the app to be downloaded to any of my devices remotely.
2. iTunes. It is still sad that I had to download something to search and install an app on a different device. Searching isn't great either.
3. Redeeming a gift card/code. In both Google and webOS, you just click "buy" for an app and then it asked you for a code. With Apple, you have to redeem the code first, and then wait for the balance to show up in your account, and then go buy the app.
4. Reversing a mistaken install. Apple - once you buy it, it's a nightmare to get a refund if you mistakenly bought it. Google - one click and it's done. This gives you a chance to make a mistake or realize it's not the app you were looking for.
5. The app information is also better, in my opinion, on Google Play. More info as to it's permissions, features, updates, screen shots, and more. Plus, I love the related apps search and results on Google better than iTunes.
Maybe it's just me, but you would think a company like Apple that prides itself on customer experience would provide a better app store experience.