In the case where the APs are placed for coverage, it's worth noting that majority of clients around the edges will have less accuracy compared to clients that are surrounded by APs.
A way to verify a client's accuracy is to check the site.xml (to launch site.xml, go to a floor plan, click on the floor plan to make the flash frame the active window on the screen, then press altogether: ctrl+x+m+l, this will launch a new window or tab based on browser prefs with the XML of the site), look for a client and look for 'discovering radios'.
Find the client mac in the XML, and then here's the important snippet:
<discovering-radio associated="true" dBm="-78" id="21881" index="1" timestamp="2013-08-14T13:09:55-07:00" valid="true"/>
<discovering-radio associated="false" dBm="-69" id="21880" index="1" timestamp="2013-08-14T13:09:55-07:00" valid="true"/>
<discovering-radio associated="false" dBm="-84" id="21870" index="1" timestamp="2013-08-14T13:09:54-07:00" valid="true"/>
<discovering-radio associated="false" dBm="-78" id="21883" index="1" timestamp="2013-08-14T13:09:55-07:00" valid="true"/>
This tells me that 4 radios hear the client, and the 1st radio is the radio of association. If you see less than 2 entries, then accuracy of client placement is less than if there were 5 or 6 entries.
Additionally, it's a good idea to make sure that the buildings have exterior walls drawn (internal attenuation is calculated based on neighboring AP signals.