Anecdotally their quality took a hit this year. After never having had an iPhone failure (and the only "family" failures of their phones being one battery dying and a couple drop-related), I've recently had:
1) June: iPhone 6 Plus battery started dying suddenly at a 40% charge rating. Took in and they said the battery had bloated and damaged the innards so they replaced my entire phone for under $100, the cost of the battery repair. Was disappointed at the failure but overjoyed at their repair/replacement response.
2) August: iPad Pro 12.9 bought in January, microphone failed. Local store doesn't stock the parts to fix it, so they swapped me for a new Pro. Again, very happy about the service.
3) September. The replacement iPhone I got in June? The screen stopped responding to touch. (Not an uncommon problem with the 6/6 Plus, apparently fixed in the 6s.) Luckily I was 80 days into the 90 day warranty on the replacement, so they swapped it again.
What this tells me is that (1) Apple's quality might be slipping, and (2) AppleCare+ is probably a good investment when I get my 7 Plus.