I originally derided the phablet craze, I argued that the iPhone 5/5s was the perfect size for a phone. The aspect ratio was perfect, the phone was big enough to make light reading comfortable but small and thin enough that you wouldn't notice it in your pocket. If you wanted a bigger app, video or internet experience, just get an iPad mini or air. Why go for such a large phone?
However after having the iPhone 6+ for a few weeks now, I've changed my mind.. The benefits of the larger screen outweigh any inconvenience you may encounter with putting it in your pocket (and so far I haven't had any issues with carrying it in my pocket) or using it one handed (which, is far more difficult, but not impossible, with this phone).
The iPhone box now only features only a blank, embossed outline of the iPhone now, instead of the pictures of the front face of the phone in prior boxes.
The iPhone 6+ will take up almost your entire hand. One handed operation is possible, but it comes with the risk that you may drop it when trying to reach the difficult to reach spots with your fingers. However, I almost exclusively type with my two thumbs rather than one handed, so the size issue is less of a problem for me. Within iOS 8, Apple also introduced a new feature to help mitigate any problems that one could encounter; Reachability. By double tapping (not pressing) the home button, it brings down home screen by 50%, allowing you to reach the top icons without moving your thumb. However, in practice, it's flawed from the outset. Whilst it helps offset the height increase, it doesn't address the increase in width (it's around 30% wider, so the icons on the opposite side of your thumb will still remain out of reach.
One disadvantage of be screen size is that you are constantly reminded of its presence. Where the iPhone 5/5s could 'disappear' in your pockets, the 6+ won't let you forget it's there. Which, if you're a forgetful person, could be useful.
That being said, the bigger screen does allow for better web browsing, reading, gaming and watching videos - the screen real estate just allows you to get more done at the same time. Furthermore, exclusive to the 6+ is landscape mode for iOS 8 - certain Apple apps, like calendar, messages and the home screen itself have either added functionality (in the case of mail, a sliding panel similar to OS X).
Battery life is remarkably better too (a beneficial side effect of a larger body) - I can get a day of full use before charging. Others may get more but I intend to use my phone constantly which probably drains the battery faster than the average user.
The iPhone 5s is tiny in comparison, and when held in the hand, exhibits an almost toy-like presence.
The iPhone 6+ amongst it's older siblings. You can see that the design has moved from the hard edged, straight line design from the iPhone 4 / 5 and back to the ergonomic curves of the original iPhone and the 3G/S.
The curved screen of the iPhone 6+ just feels much better than the hard lines of the 5 and 4. It makes the swiping left and right in apps a physical joy and the it makes the screen feel like it's apart of the body itself, rather than bolted/glued on.
A nice little bonus is the way the light reflects off the curves of the screen - it makes the phone look and feel more welcoming.
The new timelapse mode, is simply brilliant in it's design, a more in depth analysis by Studio Neat is here. Below is a time lapse video taken over the course of one night (It's two videos stitched together through the iMovie app within iOS).
After spending sometime with the iPhone 6+, I can comfortably say I would never go back to the size of the iPhone 5 - the benefits of the larger screen, better battery life and (slightly) slimmer profile outweigh the disadvantages a wider and taller phone brings. I finally see why people were/are so attracted to the Samsung Galaxy/Note lines.
Some might prefer the iPhone 6 more, the screen size jump isn't as big and the phone is slimmer as well as easier to use one handed, but in my opinion, the bigger, the better.
The iPhone 6/6+ are improvements over the already incredible 5/5s; Apple have made the best, better. So if you're thinking about getting into the Apple Ecosystem or you have a chance to upgrade, you can do so without hesitation. You'll be getting one of the best phones this year - the only thing you will have to think about is size.