How many subscribers can you have on the 5.7 advantage AP, 8.1.5 Hardware
200 is the maximum numerical limit however the real value is:
Radio capacity / Average subscriber BW up+down * AP Oversub rate - 20% overhead
Example:
Assume average of 768 down x 256 up = 1024
14Mbps / 1024 per user * 10:1 AP over sub rate = 136 - 20% = 109 users
Of course this is just an estimate. P2P, junk traffic, gaming, video streaming all eat into your 10:1 oversub rate. You probably want to start thinking about another AP at about 80 users.
250 is the max. I can send a screenshot if you like 
I agree with Jerry on the number 80 for normal internet usage.
Depends on kind of custumers and type of traffic.
We have some advantage aps with 40-60 users(corporate and cybercafes) 8-9 Mbps agregate traffic that are saturated.