I've been using RMCE-BT2 with my SE-535's in Japan for the past week. I liked the predecessor model, and this new one cleans up the small downsides of the previous one.
In particular, the noise floor on the RMCE-BT2 is much lower than the previous model. It is now undetectable, for practical use.
Battery life is much better than the previous model, and the overall refinement is very good. The pendant clip is quite effective and when properly worn you simply do not notice the wires. The symmetry of the unit is better all around for comfort and unobtrusiveness.
Overall, very good.
Zero dropout (with iPhone Xs) even when walking around parts of Shinjuku and on the JR Yamanote line trains, which sometimes bring other bluetooth devices to their knees. This might be one of the most RF-intensive environments on the planet- for example, my Sony WF1000X's slave unit routinely cut out here (and only here)- but zero issues with the Shure BT2.
Max VU level is a bit lower on this model that with the previous BT1 model, but I would venture that max volume with either approaches danger levels depending on your source material.
The battery lasted through the entire return flight from NRT to SEA yesterday, with room to spare,