Network Manager doesn't work correctly if:
* you have any wireless card other than an Intel IPW 2100 or 2200, or
an Atheros card supported by madwifi-ng
* you have a software-controlled wifi kill switch
* you have one of several different wired ethernet cards
* you require a static IP address on any interface
* you require your own DNS configuration
* you attempt to suspend or hibernate your laptop
* you need networking to work before a user logs in
"Wifi-radar" is an alternative solution that does not have all these limitations.