Caveats and hints:

You cannot login from another host into your N900 when using GPRS, at least not if it uses ppp. A lan connection (generally 192.168.x.x) will do fine.

You must setup a connection from the N900 to your lan first.

You can login as user@192.168.x.x; which does not need changes to

sshd.conf. root login is a no-no and should be disabled by default.

Paai

PS: There is a widget that displays your IP number on the N900 desktop.