So 3 months later, I went out warwalking again, and found things haven't improved any.
Offices in this complex: ~30
Total Access Points: 29
Total Infastructure Networks: 28
Total Peer Networks: 1
AP's not using encryption: 13
AP's on the default channel 6: 15
AP's on a non-standard channel*: 4
AP's using a default SSID: 5
AP's using the SSID "linksys": 4
Most AP's detectable from one location: 10
Fewest AP's detectable from one location: 2
*Non-standard channel = Anything other than 1, 6 and 11, the only 3 channels that do not suffer frequency overlap.
In 3 months, 10 new access points have appeared. The percentage of insecure access points has also increased slightly from 42% to 45%. The number of AP's using channel 6 has skyrocketed from 26% to 52%! Interestingly, the use of default SSIDs has remained the same, and the use of non-standard channels has actually dropped.