Ethernet

The ethernet driver works fine but there seems to be a hardware problem with the card (or BIOS). The card reports a new MAC address each time the computer is booted up. This can cause lots of problems because udev normally associates an Ethernet card to a device (/dev/eth0) via the MAC address, which means udev will create a new device at each boot (/dev/eth340 ...). The solution is to change the default udev association so that the association is made by device ID only (no MAC parameter in the rule).

Wifi

There are several wifi drivers for this RT3091 chip. Starting with 2.6.33, the staging rt2860sta driver contains code for this chip (there is no longer the rt3090sta driver, which was only present in 2.6.32.x), but you need to get the firmware as well (emerge linux-firmware).
This driver is not stable; the rt2800pci driver should support this chip starting with 2.6.38. So as soon as 2.6.38 is out we should switch drivers.