I have no doubt that Windows 10 will be hugely successful with consumers and enterprise users. I just doubt how readily folks using desktop/notebook PCs will adapt to the Store apps. I do think Store apps will be successful on touch-centric devices like Windows tablets.
As for a consumer app, I'll name Netflix. Yes, I have the Windows 8.1 Netflix app, but again, it lacks features available when watching Netflix in a desktop PC browser or even in the Windows Media Center program.
For the record, I actually like Windows 8.1, and I like Windows 10 Tech Preview so far. They just need to do more to convince me to get off the desktop and its programs and use the Store apps. So far, nothing in the Store has attracted me as much as the desktop programs.
The biggest problem for the adoption of apps in Windows 8 is not the quality of the app itself. The problem is that Windows 8 is a total mess and even if companies would develop great apps for the OS, few people would use them.
First, the duality and inconsistencies of the Metro and Desktop environments. I think most people ignore metro apps because every time they launch a metro app they're pushed into an incomprehensible parallel reality.
Store apps are optimized for touch, for tablets, that implies less features, lower information density, apps that don't work well with keyboard and mouse, web sites are better. Additionally, Windows 8 apps have the worst user experience ever created, with hidden menus, configuration and search, without any indication of how to find those elements. Too much white space that is excessive even for touch.
I think Universal apps has an opportunity to succeed in Windows 10 because the duality of Metro and Desktop environments is removed, the apps integrate beautifully in your familiar Desktop user experience. Most of the flaws of metro are being corrected, and apps will be better designed for mouse and keyboard interaction, maybe some companies could even fork part of the UI to target each form factor.
Microsoft has to give developers some advantages over websites too. For example, for developers, discoverability through the store is important. The store provides a secure payment system so you don't have to implement your own. Store apps are secure and can be installed without worries, distributing old x86 apps has big security issues. The great benefit of having a little piece of the user's start menu to showcase your content and increase the engagement. A lower cost of development to achieve a superior result without having to test the app in every single browser and their inconsistencies that are changing all the time.. and more.