Not impressed!
I had experience of this 22 Feb LHR-GLA and 25 Feb GLA-LHR.
My ticket was in Group 1 for both legs.
On arrival at the LHR gate, it was impossible to tell which queue to join due to the number of people pre-queuing. Only possible to figure it out by walking to close to the front of the queue and then following it back to make sure you joined the right one.
GA called forward groups 1 and 2 to board trhough the e-gates. They then called forward goup 3 to go through the manned entry. The e-gates weren't working so they then had two people and three groups of passengers to manually scan. Except they didn't stop annoncing that groups 1 and 2 should be using the e-gates.
Flight took an age to board, and left about 20 minutes late.
Similar at GLA. Couldn't tell which queue I was supposed to be in due to signage being right by the gate door and the queue snaking quite far back. Some people let me slip in front of them as I was lost as to where I should be. They called forward group 1 and, by the time I got to the group 1 lane, they were calling the next group forward and I was tutted at for queue jumping.
Again, flight took ages to board and departed late.
My partner does GLA-LHR or GLA-LCY quite a bit and hates the new system. Hasn't had a punctual flight since the trial started.
I got a few feedback surveys from BA and made sure I commented on how I didn't feel the process led to an efficient way to load the aircraft. Too many people with decent status on commuter routes makes the groups pretty much pointless.