I had some problem with the drivers from sourceforge (RT2500 chipset), the wifi interface automaticly went down after a few hours so I often had to up the interface. Plus, The wifi interface is not "configurable" via the wireless shortcuts (like wireless_mode etc..) so I had to use the iwconfig command for each parameters. I haven't tried the official driver from ralink thougt. Now I use ndiswrapper instead and it works fine. I also use a D-Link DWL-G50 rev.B (rev.A is an other chipset), it's ok with madwifi.
Jonathan Marchand
