Originally Posted by Spoonrobot

The initial generation of 5800 was a step back IMO. The front derailleur has a tendency to cause over-shift situations very easily compared to 5700 and was much more sensitive to height over the big chainring than previously. They tried something new with the longer lever arm and FD-5800 just did not work very well, they also didn't last very long. We were getting FD-5801 way earlier than I expected. The improved derailleur is much better but AFAIK is not as widespread on OEM bikes, yet. The shifting both front and rear was also not nearly as crisp and tactile as 5700 or even the updated lower end groups. Rear shifter has a tendency to shred cables and this ends up with fragments that contaminate both the housing and shifter body. Any cable replacement for 5800 will almost always require a housing replacement as well. This gets expensive when the cables only last 3,000 miles. Both R3000 and R4700 shift much better, this means both faster and with better tactile feedback to the fingers. 5800 shifters just didn't last as long either, our high mileage guy had his wear out in a little less than a year, something like 14,000 miles and his were done. Previously he'd been using 5700 and they'd gone at least twice as long. I'm working on another 5800 bike that has shifting issues that haven't been fixed by housing, cable and derailleur replacement that most likely will be a shifter issue - less than 10,000 miles on that one.

Sorry if this is confusing or hard to read; my wheelhouse isn't made from words so sometimes I have problems.