It’s wonderful.

Once set up it works faultlessly and doesn’t require the readjustment or cable servicing that’s required with a cable operated drivetrain[1].

On top of that the front derailleur constantly trims itself to never chain rub and semi-automatic[2] shifting is surprisingly useful.

Also Di2 let’s you add multiple shift buttons. So you could have shifting at every hand position if you wanted.

Finally the thing that sold it to me. I did a multi-day ride on my old bike. After the first 4 days I got cramp in my hand everytime I shifted. Told myself I’d try di2. Every gear change is now as soft as a mouse click.

All that and the only real downside side is you have to change it every 6 months.

It’s a very well thought through system. I know lots of people with Di2 in my bike club. I don’t think anyone dislikes it.

1. Bowden cables don’t “stretch” as such, what actually happens in mechanical systems is that the ferrel ends settle over time or the linings of the cable outers wear and flake causing friction.

2. The semi-automatic mode means single buttons for higher or lower shifts. The front derailleur shifts as appropriate to give you the next ratio.

You can repeat that on each hand or on the top hood position. So for example, if you want to change gears as you indicate left or right, now you can.