There were a couple of app-related issues that caused me to return my Lumia 920, much as I loved the hardware, and much of the OS. Far and away the primary app-related reason for leaving, and staying away from, the WP 8 platform, is the utter unreliability of the only halfway decent PDF reader app available, the one from Microsoft. Simply put, it is garbage. I never knew what would open okay and what would fail. That's a show-stopper for me. I'm itching to buy another Lumia 920, but until they either get their own app fixed, or better yet, just get Adobe to write one (I mean, my God, they have one for WP 7.5!), I just can't do it.