Here are my thoughts about the iPhone 8 Plus, Space Grey
Design
Sure, this is a 4 year-old design. But I have to say it, I love it. I didn't like the iPhone 6 when it was announced because of its back. The antenna bands and the misplaced camera / corner radius made the phone look weird. Apple has had 4 years to refine this design and it shows. The glass back brings back those vibes from the 4 and 4s, while retaining the rounded look (to which I prefer) of the 6/7 lineup. I bought the Plus. However, this phone is so well designed that, for the first time in my life, I would not mind to buy the white iPhone 8 despite the white front, solely because of its back. I love the white back / black Apple logo combo.
Battery Life
Coming from a 6s, I have to say battery life feels great. Granted, I got lucky with my unit (Coconut Battery shows an extra 100 mAh than the supposed factory capacity. Still, the phone lasts 10 hours, easily, even doing some medium to heavy use. I downloaded my music library, made a 1h05m and a 43 minute facebook video call, 30 minutes worth of audio calls, plus normal use (mostly social media and apple music) for the rest of the day (from 11 A.M. to 9 P.M.). The phone started at 93% and ended up at 18%.
If you own an iPad, you don't need to buy a new cable for fast charging. It took one hour for the phone to go from 18% to 83%, WHILE indexing the photo library and analysing faces. I used a 12W iPad connector last night. Today I may report how fast it charging with no background tasks.
Performance
Performance is great. However, the newness of iOS 11 and the lack of Pro Motion display shows. With future updates, iOS will become smoother, but I feel that a phone this size should have Pro Motion. 120Hz really shows its difference in larger sizes. I didn't notice a reduced frame rate in my iPhone 6s and iPhone SE in both iOS 10 and iOS 11, when compared to my iPad Pro side-by-side. In contrast, the reduced frame rate is apparent when comparing the 1st generation and 2nd generation iPad Pro even when not next to each other. The 5.5 inch screen is big enough to tell the difference between a 60Hz and 120Hz display.
Apps seem to hang out mid animation for a couple of nanoseconds. If you don't own an iPad Pro, you will not notice this (confirmed with people that don't own one).
Cameras
The cameras on the Plus are absolutely fantastic. The most noticeable update from my 6s. Not much to say about this.