I spoke with the barrier staff earlier in the week (in between the mad rushes!) to ask how they were finding the new arrangements and how passengers were responding.
Firstly, I can confirm that platform announcements were being made earlier than in recent months, at around 20 minutes before departure, though not consistently so, ranging from 25 to 15 mins.
The control of valid entry, in advance of a departure, can be regulated from a terminal behind one of the pillars along the gateline, and even if one of the staff is slow to 'authorise' a forthcoming departure, the first passenger attempting to use a ticket for that departure will flag up the attempt and the supervisor will be able to respond by 'authorising' tickets for that departure.
This can create the mistaken impression by the passenger who takes their rejected ticket and tries in the next gate (by which time it will have been authorised) and thinks that one gate worked and the other didn't!
Apparently a lot of passengers have been complaining that 'the barriers made them late' which, after observing several rush-hour departures, I find hard to accept.
One practice which does cause a lot of confusion among passengers is the regular changes in direction of flow though the barriers, set, reasonably enough, to maximise flow to suit demand. (eg when there is an arrival, a whole block of gates will be set to allow exits (and a few for entrances) and when departures are announced, a whole block of gate is set to allow entrances.
This confusion can arise as these changes to the flow through these blocks are made, and the difficulty for passengers in recognising which barriers are set for each direction - especially in a dense crowd, until you are closer to them. Its being managed by staff who usher and direct passengers towards the 'open' block of gates, but until passengers realise and become accustomed to the direction of flow being alternated so regularly, it will remain chaotic. This seemed to be quite effective, though does involve a lot of shouting "This way please" several times. Even once passengers know and expect the flows to be changed from minute to minute, there is no indication from a distance which way to go - its only when passengers are close enough to see the green arrow or red cross on the gate's display that they will know which block of gates are open.
The staff ushering passengers will be needed throughout the time while the barriers are in their present position.