have you heard of fim facebook? i think its superior to the regular winmo app. it allows real time chatting and utilizes m.facebook.com. its also extremely lightweight. when you first login theres an ad on the top, but u can click it, then close the window, and it disappears. give it a try!
http://forum.xda-developers.com/showthread.php?t=480365
if you found this helpful, a thanks would be nice!