One problem I found was that NetworkManager would re-prompt me for the wireless AP password every time I logged in. NetworkManager's nm-applet program (the GUI half of the system) uses Gnome's keyring system for storing passwords. Because I wasn't running in Gnome, however, the keyring daemon wasn't being run on startup. As a result, errors like these appear on the console:
** (nm-applet:6925): WARNING **: Error saving passphrase in keyring. Ret=2
These problems persisted even if I started gnome-keyring-daemon manually or added it to my .xsession file. Anyway, I found the solution to my problem. This is what my .xsession now looks like:
eval "`gnome-keyring-daemon`"(On startup, gnome-keyring-daemon prints two environment variables that must be added to the environment nm-applet runs in; I evaluate the output so that they are added).