just found this article. I remember reading someone set roaming to highest, but seems like it applies more to your adapter finding a better router/ap to connect to as oppose to maintaining a stable connection. This may be relevant.
http://www.intel.com/support/wireless/wlan/sb/cs-006205.htm
My only concern about turning off power management and maximizing transmit power would be battery life. Seems ridiculous I need to maximize this setting when my router is sitting on the floor next to me. I think last thing I have put off trying is ethernet cord before I dump this card.