Thanks to IvD, I got my rt73 device working with wpa_supplicant with the in-kernel driver in 2.6.24. I removed the legacy rt73 driver package from my system and the connectivity promptly disappeared. After some research, it turns out this was due to the CVS rt73 driver package providing firmware in /lib/firmware.
Is there any way around this, or is the legacy rt73 firmware currently required in order to use the in-kernel rt73 driver?
Firmware is needed whatever driver you are using even if you are using M$ OS. In this last case, they are often built in the driver himself.
Can the in-kernel driver provide firmware though? It seems like if using the in-kernel driver, you must also be careful to place firmware in /lib/firmware.
You can download the firmware files from the Ralink support website.
Ralink recently added a license to the firmware files, so hopefully distributions start packaging the firmware files in their package repositories soon.
Ok, I'll file a bug with Gentoo.