I would like to upgrade my iPhone 4 to iOS6 but I'm wondering if I will get performance loss (as when I upgraded my iPhone 3G to iOS4 : terrible). Can someone confirm that it won't affect my day to day use?
I have been running iOS 6 since Friday night (I ran the Golden Master that became release) on my iPhone 4.
Safari feels snappier (and show improvement on SunSpider benchmarks).
I have not noticed any degradation like the 3G iOS 4 craziness that apple gave us (I went through that as well).
I am very happy and using it (everyday) and it feels a bit better in most things than 5.
I have an iPhone 4 running iOS 6 and haven't noticed any performance or battery life issues. In fact, the phone is 18 months old (so the battery isn't new), and before charging it earlier today, it was at 14% battery with 2 days 20 hours of standby, 5 hours 30 minutes of usage. I'd say that's pretty good!