Thanks for starting this thread.
Jury's still out for me. I'd been using the iPhone 6 since launch and have been pleased with it. I used a 5s previously. We also had a Plus ordered on one of our lines and it shipped early before I could cancel the order.
The day before the Plus arrived, after a day of heavy (but not extreme) use the battery on my iPhone 6 died right before dinner while I was out without a backup battery. After reading all the reports of how great the battery life was on the Plus, I decided to try it once it was delivered and see how I'd adapt to the size (which I had determined was too big for me based on visiting the Apple store a couple of times).
That was yesterday and, as I've said, I'm still undecided. The iPhone 6 is a pleasure to hold and use, but the screen on the Plus is a bigger improvement for me than it appeared to be in the Apple store (especially for web surfing). I was able to take the Plus out on a 7 mile run yesterday and it proved only marginally more effort than it did with the iPhone 6. The battery got me through the day pretty easily, albeit it wasn't a full day.
The plus fits in all the pockets that I've tried so far, but I definitely notice it in those pockets. I notice the iPhone 6 more than the 5s, but not as much as the Plus. Using the camera on the Plus is more enjoyable than on the iPhone 6 apart from the OIS – it's the additional screen size that makes for an improved shooting experience. And now I kind of see why people like using their iPads for photography (though I've never thought to do so myself).
When the battery died on my iPhone 6 the other day, I thought about what it would be like using that phone with a mophie, and that combination seems much more unwieldly than using the Plus (assuming, of course, that it won't require a mophie). The advantage of using the iPhone 6 with a mophie is that I'd only only need the mophie for days when I know I won't be in the car or at my desk much, so there's the option to have the smaller form factor. With the Plus, I'm carrying the extra battery capacity whether I need it that day or not.
Again, jury's still out for me. I was pretty certain I was going the iPhone 6 route until a couple of days ago, but now I'm undecided.