I absolutely love my 7 Plus. The new camera is best-in-class, the speed with the extra gig of ram and new processor, the stereo speakers, water resistance, and the new colors (I chose matte Black/Black) is well worth the upgrade. My 6S Plus was plenty fast but the 7 Plus ups it to speeds I've never seen on any other smartphone. No lag, no problems, great battery life. Some people are having trouble with theirs but mine has been rock solid. I don't mind the removal of the headphone jack, it's of my opinion that it will become a thing of the past and that Bluetooth sounds every bit as good and it's 2016, the future is wireless. The fact they were able to do stereo speakers too was just icing on the cake. I personally use a combination of bluetooth headphones, chromecast audio, and the built in speakers depending on my mood that day or the application. It works just fine.
I upgrade iPhones every year though. I went from 6 Plus to 6S Plus to now a 7 Plus and will do so for the forseeable future. I don't like being behind the curve and while older iPhones get updates (much better than the competition), I find the new exclusives to be worth the upgrade. iPads I generally upgrade every 3 years and Macs every 4 years. I find they don't need changing as much. I also tend to find the changes aren't as big from year to year. This year will be big for Mac.
Ultimately, I feel while they did keep the same construction, the changes this year were more than enough of a reason to upgrade, IMO. They are selling like hotcakes now and I see why. It's a great smartphone and this year is no exception.