I think Apple did a great job by releasing iPhone 6 and iPhone 6 Plus because Apple's competitor Samsung is popular for the big screens. But I don't think it was a good idea to release iOS 8 because it's full of bugs. Also there are almost no differences between iOS 8 on iPhone 5S and 6, 6 Plus. But I think it was a good idea to make bigger screens. Here are some other reviews you would want to check out:
1.http://www.techradar.com/reviews/phones/mobile-phones/iphone-6-plus-1264566/review
2.http://www.techradar.com/reviews/phones/mobile-phones/iphone-6-1264565/review
3.http://www.macworld.co.uk/review/iphone/iphone-6-plus-review-apples-big-screen-benchmarks-tests-photos-3534919/
1.http://www.techradar.com/reviews/phones/mobile-phones/iphone-6-plus-1264566/review
2.http://www.techradar.com/reviews/phones/mobile-phones/iphone-6-1264565/review
3.http://www.macworld.co.uk/review/iphone/iphone-6-plus-review-apples-big-screen-benchmarks-tests-photos-3534919/