I have an iPhone 4, and use all the features. I'm planning on getting a 6 in a couple months, or maybe wait for the 6S. In the mean while, it still does the job for me, only Facebook is painfully slow. I think Facebook optimises for more RAM or more cores, because it will just sit there, without the downloading indicator showing, and then suddenly show content. I'm definitely looking forward to a larger screen, but in the meanwhile I just use other devices if I need to use a complex non-mobile website. What's kept the device usable is everything going through iCloud, so I can do most of the data entry on something larger, and then view data and do smaller edits on the phone.