My own opinion is I wouldn't pay $900 for an upgrade from the 105 R7000 to the Ultegra R8000 series. I have the 105 on my Trek FXS6 and I have ridden several Ultegra mechanical. The performance is very, very close. Sure the Ultegra might be a bit "tighter" in shifting performance...but not $900 better. The thing I would pay more money for is Di2. I have the Ultegra Di2 system on my road bike and that's worth the extra coin.