Words against words, but it is laughably big. Humongous.
It's a 5.5" device. Of course it's big.
Laughably big? That depends on the perspective. You could say the iPhone 5S is laughably small, a smartphone for ants. And coming from the 6+, I would tend to say that.
Now, there are other phones on the market that have sold well for years (Samsung's Note line, for example), which means there is demand for a big phone.
There are multiple advantages to owning a big smartphone, just as there are for smaller ones. If you do a lot of calling, I'd go with the smaller devices (even 4.7" for some people is way too big, hence the hype around the 5se or whatever it will be called).
If you want a phone that also doubles as a great way to consume media, then the Plus models are fantastic (which is my usage pattern - I rarely make calls and don't spend hours on the phone).
There are compromises for everything. On one hand, Plus owners get a better camera, more battery life and a better screen (1080p does make a difference). On the other, it won't fit in every pants pocket. But at least for me, I will take that drawback over multiple benefits any day.
I used an iPhone 6 for a while when it came out: the screen quality was not as good and I couldn't even get a full day of usage. The 6S did not improve that. If the 7 does, I might go smaller, but it's not likely. Apple would need to improve the screen to 1080p at least.