I got it for my road bike not knowing anything else than I did not have to push so far in and experience wrist pain on the very long rides and I'm super pleasantly surprised. I got the optional bluetooth module and I can change modes from my phone. And you don't need the phone to do trimming or switching between whatever 2 pre-programmed modes you setup. I have mine setup to auto shift the front ring. Those stories about people getting stranded because the battery runs out...well if you run just about any modern GPS unit, you can get Di2 battery status (as well as other stuff) on the screen so there's no excuse to run out of battery. I used 10% in 10 hours on the Tour das Hugel (lost of shifting front and rear ring). Normally I can go many weeks without charging. The other cool thing, if you're into ride data (I am) you also get things like HR and/or power vs gear and hill grade, etc. I'm sure there are other cool things I haven't discovered yet. Best of all, my wrists thank me for it.
If I'd have waited a few months, I could have opted for the SRAM eTap wireless. On the positive side, much cleaner cockpit. However having to charge multiple batteries may be a pain.
I love the polished uppers on the fork of that Scott!