I'm actually not that great at technology and computers and stuff like that. What I like about the Apple system is that it's easy to use and quite intuitive, as well as the fact that it looks nice! Really I just need a phone to call people, use as an alarm clock and play a few games on, and the big-screen iPhone 6 Plus would be great for gaming. I like to play bingo sometimes, which works well on my smaller iPhone 4. But the site I usually play at is good for more than just bingo games, with slots and roulette as well, so the big screen would make everything much clearer.
This is the most important difference with the new iPhone - the screen sizes. The old phones have started to look a bit small now that so many Android phones from Samsung and other companies come with bigger screens. The smallest iPhone 6 screens have gone from 4" to 4.7", which might not sound like much but makes quite a big difference to the screen area. The iPhone 6 Plus is 5.5" diagonally which is pretty big. You could easily watch movies on it!
Another thing I use the iPhone for is taking photos, and the new phones have a good camera in the usual place and an improved front-facing one for taking selfies and doing video calls, if that's the kind of thing you like! I think the existing camera on my phone is fine, so if the new one is better, that's great, but it wouldn't be enough to make me rush out and buy one.
I think that right now, the iPhone 6 will be too expensive to convince me that I "need" it. When it's released in Malaysia the price will be something around RM2,500-3,500 without a contract. If I was going to upgrade my iPhone 4 I'd probably think about getting an iPhone 5S, as the prices of these will probably now start to come down. The only problem is that big screen - if I get to try out someone's new iPhone 6 my old phone is going to feel very small...!