Hi Si,
They work just as well as standalone APs, you get all the internal technology and if you had just one it wouldn't make a lot of sense to have a controller however if you go 3 -4 access point you really need to have a controller in the middle who will manage the access points, control users centrally report to you.
If access points operate on their own they don't know about each other only that there is another guy on the same ssid.
You won't have any challenging of users on the network by 802.1x, captive portal pages etc.
Robert