Comment 6 for bug 130786

The latest developer comment about slow rescans is as follows:

 Comment #8 from Dan Williams (NetworkManager developer, points: 18)
2008-01-23 22:31 UTC [reply]

r3262 of the stable branch fixes some deficiencies of the scan algorithm. NM
will scan every 20 seconds for 2 minutes, then bump the scan interval up every
120 seconds thereafter. If the device is deactivated, NM will bump the scan
interval back to 20 seconds for 2 minutes, then up to 120 seconds thereafter.
If the user interacts with the NM applet, NM will bump the scan interval back
to 20 seconds, and immediately scan if no scan was done in the past 20 seconds.
 This should fix many of the complaints about the speed of updating.

The other issue might be the driver; some drivers (especially mac80211 based
ones in recent kernels like ipw4965) are still buggy and don't report complete
scan results when asked to scan. You can test this by executing (as root)
"/sbin/iwlist <wlan interface> scan" and seeing how many APs you get back, and
comparing that against how many you expect to get back. If the driver is
broken, then NM certainly isn't going to work very well.

I think that those changes are probably a great solution to the issue, so I've asked which version of NetworkManager includes those changes, and will make note of that here when I get a response.