Now made a few trips from this new airport and it certainly needs some major rethinking.
The previous posts about the exiting fiasco are pretty much spot on and on balance Don Muang was IMO more passenger friendly.
Departing is not that much better either. Despite the abundant space there are too many bottlenecks. Only limited availability of departure tax booths being just one.
What I do find disappointing is the lack of any facilities once you have entered the concourses. Even accepting there is still a lot of work to be finalised which is evident by the amount of building material scattered everywhere, there doesn’t appear to be any provision for any facilities within the concourses once you’ve cleared security.
Others have commented on the marathon walks, lack of signage and the unbelievably slippery surfaces; however the worst thing is the greyness. Everything is either bare concrete or painted grey. It is so depressing.