The RB532s start showing large latency variations (high jitter) if you use WDS. Although, we haven't tested without WDS to verify this. The latency issue starts showing up after about 3 associated clients.
I can can't directly confirm this... we use 532's/SR5's for APs, and 112's/CM9's for CPEs...
it seems that WDS may add about 5-10ms, of latency, presumbably due to CPU, but that's not the real issue
While NStream makes things much more consistant for latency issues (large spikes and contention/hidden node issues are eliminated), it has a downside... because the CPE's only transmit when it's their turn, if there is any interference that causes the CSMA/CA subsystem to wait before transmitting, the radio can actually miss it's turn to transmit. (MikroTik seems to have commited to trying to turn this off in a new version of NStream for v3.x, but they've not clearly and specifically said so yet, but they have said they are looking into it...).
It is our experience that with NStream and polling, you can put 25 customers on a AP, more of less regardless of the load from any individual customer, and all customers will have a reasonably consistant and reliable service with accecptable ping times.
when using polling, average ping times seem from AP to CPE seem to be roughly related to the number of radios associated to the AP, so if you have an AP with 7 users, average ping times would be between 5ms and 10ms. when we put 25 CPE's on one AP, our average ping times to the CPE are usually between 20ms and 25ms.
I think this is because the more radio's associated, the longer between polling intervals, and therefore the more pronounced the wait is if the CPE misses one or two time slots for transmitting.
Since WDS increases the number of un-necessary packets transmitted, with it being a full bridge, this adds to the problem as it will sometimes be waiting to transmit the traffic that would have otherwise been blocked if you didn't have WDS, and so your real traffic sits in queue and waits it's turn... This part of the problem would go away if you didn't have WDS and had off Default Forward, then only CPE to AP communicatins would ever be transmitted, and never anything CPE to CPE...