Spinning data wheels in Safari, landscape/portrait lock-ups, screen freezing, random unresponsive touchscreen, worse battery life than the previous update, app crashes (worst ever in any version of iOS for me)...all of these things make for a bad update in my book. Perhaps the 6+ is affected more than other iPhones?
I can relate to the spinning data wheel in Safari, but that has been a thing with my iPad since early version of ios7 other than that my iPad4 has 10-11 hours usage per charge and a few minor now and then blips in the road. In my case 8.1.2 has worked well.