I was provided a new iPhone 6 through my work and it's like night and day compared to the abomination that was iOS 7+ on the 4s. I haven't seen any significant signs of the refresh problem on the 6 yet (running 8.1). This is very likely due to the extra RAM in the 6, although one of my earlier posts had shown that the refresh problem was fairly easy to replicate even on an iPad Air, which also had 1GB of RAM. So I was skeptical when I got my 6 and expected to see some similar signs of refresh problems, although to date I have been pleasantly surprised and haven't noticed any significant problems.
I have been able to load multiple tabs in Safari and switch between them without them reloading. Of course there is a point at which too many tabs result in too much content to hold in memory, at which point a tab will eventually refresh.
As for app refreshing, I have been able to load multiple apps, across multiple days, and switch between them without the apps refreshing. I can load up a map in Google Maps, switch to my email, load multiple web pages, check Facebook, and come back to the map without it refreshing. On the 4s, just switching between two apps would more often result in the app I returned to refreshing.
I have pushed this to the extreme with many apps, each loading lots of content. Eventually apps will refresh, but when they do the apps load extremely fast and the content reloads quickly.
Overall using the 6 is like a breath of fresh air. This doesn't reduce my frustration over the introduction, and lack of resolution, of the problem on the 4s with iOS 7. If my work hadn't covered the majority of the cost of this device I doubt I would have upgraded to another iOS device. And I have no plans to update my 4s to iOS 8.1. Its limited resale value will be higher if I leave it on 7 (and would have commanded a much higher premium had I left it on iOS 6).
I am concerned that they chose to stick with only 1 GB of RAM on the 6, however. I'm not convinced that I won't be running into similar problems in a couple years when iOS 10 comes out with much higher RAM requirements.