I flew in 30A on LHR-KUL two weeks ago. Overall I agree with the mixed reviews, the seat worked well for me but it might not for everyone else. I'm 6'3" and average in build.
Good:
-Near unlimited legroom, exit door did not impede on this so not sure why this is mentioned. You can actually prop your leg up on the door which I did for a while to stretch.
-No pax stepping on your feet waiting for the toilet (which happens in the aisle seat)
-Very little disruption from the toilet despite it being close by
-First served meals in the Y cabin
-Hard divider between seats means you don't feel the person next to you moving as much
The not so good:
-The seat is narrow. No way around it. I found it tolerable, but not comfortable. At times my shoulder hurt as I had it wedged against the cabin wall to give the person in the middle seat more space. However the extra legroom made it much better than a normal seat for me.
-The IFE screen on an arm stowed in the seat is OK, but I find with BA many times they are loose and you need to position them carefully or hold them continuously, otherwise the screen falls down.
If you are slim to average in build, the seat is fine. For those a bit larger, give the seat a miss.