I just received my 6+ today and for about an hour I was unsure what I thought. In the end, I think it will be fine.
Things I like: Screen, battery, camera, it is something different (I don't think the iPhone 6 is that much bigger than the 5). I think over the next two years, developers will take more advantage of the screen size. I'm also interested in what jailbroken type apps will show up.
Things I don't like: It is a bit heavy, pocket ability. It is a bit difficult to use one-handed but not totally impossible for me.
I think in a few days, I'll be used to the 6+. I went to an ATT store to look at a 6 and the icons and text seemed small. My old iPhone 5 looks crazy small. I wish Apple had made something in the middle like a 5.1" but if I'm spending as much money as I do on an upgrade, I want the new phone to be significantly different to be worth upgrading.
I saw a couple of people looking at the 6+ and I showed them mine. They of course asked, "Is it bent? I heard they bend." In my opinion this bent thing is out of hand. I haven't had any issues with mine all day being in my pocket and I haven't tried to be particularly careful with it or anything. I do have the Apple leather case on it which I think feels nice.
Just my $.02