The best fix for issues people are having is to flash it with the latest firmware and load the latest Nokia system apps. Resolved all issues on the two 920s in my family (one still had odd resets and the other bricked itself during a hard reset). Everything including Skype runs perfectly now.
I don't see a lot of point in the 820 with the 720 just around the corner... depends on the pricing.
The 620 is also attractive and cheap too.