I want to contribute with my impressions from the first couple of rides:
- Installating the GeX was absolutely no problem. As many others, I didn't need to bleed the brakes after shorting cables. With dropbar-integrated cables, it's difficult to fit the cable into the Brifters. I recommend to completely unscrew the Brifters from the (tightended) clamps for fitting the cables, makes life much easier...
- Adjusting the deraillieur was absolutely no problem with the app. Just make sure to first set the limit screw for the smallest cog, and start the adjustment in this cog moving your way up to the largest cog.
- Once set up, shifting performance is very good. The smaller button on the right brifter is at first a bit difficult to "find". But as there's also a button on the left, you don't actually need it.
- I'm running it 13-speed with a Ekar 9-42 cassette. So (quite obvious), the derailleur works well with a 9 T cog (Wheeltop website states 10-11 T for smallest cog). I'm using a 12-speed flattop schain, so I can't say anything regarding compatibilty with Ekar chains. However, I wouldn't expect any problems.
Overall, I'm super happy with it!