We have a little bit of this concrete walls business, too. The solution is a lot of APs, which means more cabling and PoE switches. This also means more expense, but happier users.
We're using Ubiquiti Unifi WAPs, which are, in my opinion, the best and cheapest on the market.
I agree, at work we also use a lot of Ubiquiti Networks Unifi Pro APs.
It is an old building, most of the walls are the brick and mortar, but some are concrete as well. The walls are quite thick, usually about two of your US feet, or about 60 cm
The APs work quite well for the price. I really like the central administration, one server to rule them all, overview, distributed firmware upgrade etc. And I still can SSH to an individual AP etc. The performance is very good, and the penetration through walls also is quite respectable. With one in every room you get the 5 GHz coverage there, and the 2.4 penetrates a couple of walls and floors too. In fact, our biggest problem has been that the range has been too good, people way to far away have been able to connect and use the AP:s, witch can degrade performance for the rest. That is a feature that has been very much requsted, ie that the nodes automatically drop connections that are too weak. I *think* that was implemented in a firmware upgrade a while back, but I can't swear by it as I'm not the head maintainer of that network. Also we run an open network, it is free for our customers, we don't mind that people around our locale and in the same building use our network as long as it doesn't degrade the performance for our customers.
Sure, super expensive Cisco stuff probably is better, but Ubiquiti has impressed me so far with the very reasonable price and performance.
If you want wifi, I'm all for drilling holes in walls and route wired network cables throughout everything, but I've noticed that wifi coverage seems to be expected nowadays.
Intolerant people ought to drink more beer.