From what I've seen, the lack of RAM seems to present itself as being worse on the 6 Plus. Not sure if it's because there is more simultaneous content on the screen, or because it does the scaling. But it is not ideal.
I am very glad to hear the rumors that Apple is focusing on optimizing and speeding up iOS 9. It needs it. I am also hopeful that they might be able to port some advanced OS X technologies, such as RAM compression, to help us get up to 1.5X the RAM, depending on usage. However I don't know enough about the technology to know if it's feasible on mobile devices. It may require a bit of CPU overheadas normal compression often does. However, this could be less of an issue with the A8 or perhaps the future A9 chip.
Besides that, the biggest downside for me has been the lack of third party support for the larger displayespecially on the 6 Plus. Apps aren't doing much to take advantage of the extra spaceunlike they do on the iPad. This was a fairly significant selling point for me, especially as I replaced my iPad Mini 2 with the iPad Air 2. The display itself is gorgeous and pretty good for watching video content. But outside of that and Apple-apps there isn't much reason for it. Even the sidebar content Apple uses seems superfluous.
I'm also not overly impressed with the optical image stabilization on the 6 Plus. It helps, but not to the extent I thought it would. I could do without it next time, especially if the iPhone 6S doesn't have it as I'm definitely going back down in size.
I am very glad to hear the rumors that Apple is focusing on optimizing and speeding up iOS 9. It needs it. I am also hopeful that they might be able to port some advanced OS X technologies, such as RAM compression, to help us get up to 1.5X the RAM, depending on usage. However I don't know enough about the technology to know if it's feasible on mobile devices. It may require a bit of CPU overheadas normal compression often does. However, this could be less of an issue with the A8 or perhaps the future A9 chip.
Besides that, the biggest downside for me has been the lack of third party support for the larger displayespecially on the 6 Plus. Apps aren't doing much to take advantage of the extra spaceunlike they do on the iPad. This was a fairly significant selling point for me, especially as I replaced my iPad Mini 2 with the iPad Air 2. The display itself is gorgeous and pretty good for watching video content. But outside of that and Apple-apps there isn't much reason for it. Even the sidebar content Apple uses seems superfluous.
I'm also not overly impressed with the optical image stabilization on the 6 Plus. It helps, but not to the extent I thought it would. I could do without it next time, especially if the iPhone 6S doesn't have it as I'm definitely going back down in size.