I ran fair number of tests using the proto's BLE interface with LabView. While the radio seems a bit weaker than the other two BLE meters I have looked at, it seemed to work alright with the firmware I was using.
Which I assume is v2.00?
I am not sure if I did much testing beyond 1.26, if at all. They were making changes to the filters during that time and I was running tests to evaluate them. The BLE interface wasn't working originally on the prototype meter, so I was using the card to log the data. Using the firmware supplied (pre 1.0 really early stuff), logging to the card would hang but once I had 1.0 loaded, it seemed fine. When I first started working with the BLE, I had some problems but discovered this was with my code, not the 121.
I had several posts in the Issues area documenting my findings but it seems it was getting a bit too cluttered for Dave so I cleaned them out to help them with their bug tracking. These were fairly long tests I was running and I don't recall having problems outside the range being less than expected.
I didn't want to invest more time until at least the hardware had settled. Dave had mentioned some of the changes they were making beyond addressing the shim. It seemed like they were moving in the right direction. It's been a while since I have seen him post any more about it. Maybe next year...
If you do have problems and decide to roll the firmware back, just keep in mind the changes to the filter I mentioned. You can see from the attached plot how they were playing with the roll off.