I received the new DN110 battery and MT800 display and installed them today. It's mostly good news but there are some minor glitches.
First, there are only 2 options to get synchro shift.
Option 1. Synchro Shift without Wireless Connectivity
This requires both the new BT-DN110 battery and SC-MT800 display. I installed the new battery without the display and e-Tube couldn't make the Bluetooth connection. Although disappointing, this makes sense because the default shift mode is "Manual". The display allows the user to choose Manual, S1 (syncro) and S2 (synchro).
Option 2. Synchro Shift with Wireless Connectivity
This requires Option1 plus the new inline wireless unit (EW-WU111). The EW-WU111 replaces the D-Fly transmitter (EW-WU101), and adds Bluetooth to ANT+ connectivity. The EW-WU111 ($80) is usually externally mounted near the rear derailleur. This option allows a smartphone or tablet to update Di2 settings.
Even if you go for Option 2, it's better to do the 1st installation with a wired connection to your computer. It's easier to do the firmware updates and change the Bluetooth password. The BN110 needs to be updated to ver 4.3.4 and the MT800 requires ver 4.2.3.
As for the mapping, I suggest mapping S1 and S2 as full-synchro (eg. flat vs hilly terrain). The semi-synchro mode doesn't prevent cross-chains, and it's too easy to go big-big when doing a sweep of 2 or 3 gears. The other reason is that you can still manually change the front derailleur in full-synchro mode.
This brings up a quirk in the gear mapping (see attached). It's easy to change the cross over point in the small ring (eg. 34). I can get it to upshift to the big ring in gear 5 to 11 (smallest cog). However, I can only get a synchro shift from 50T to 34T when the cassette is in the 10th gear (2nd from largest cog). I can't seem to get the front derailleur to cross-over at a lower point (eg. 50 x 23). To get around this, I'll just manually shift to the 34T when approaching a steep climb or rolling terrain.
I only had time to go a short ride but the synchro feature is awesome! I'll do more testing to fine-tune the cross-over point.
A nice feature is that S1 or S2 will double-beep when the next gear change will shift the front derailleur.