I notice that the unit's yellow LED is slowly flashing. Should I be concerned? What does it mean? What do I need to do to make it stop?
The yellow LED indicates 'activity'. If it's not on, the system is idle (you'll notice by the lack of fan noise too and if you have a power consumption meter, you'll see it drops to 30 Watts). Since the summer all revisions of the firmware image make this image flash on and off instead of being constantly on, it's a know "issue" but it's nothing to worry about. Just look at the BTC Guild stats, over 8h it should give you a reasonable good picture of performance, giving you about 0.045 BTC / day