Mine just arrived today. I can't wait 'til I get to put stuff in it and use it on a trail. I don't have anything to go in it right now, but multiple visits from UPS and the USPS during the next few days should fix that problem. The Mule seems to be very well constructed and a good value, especially at $30 (gotta add shipping) under the $80 MSRP.
You can only get it in red, but I like it because it doesn't look bad at all and it's a pretty good color for visibility as opposed to the black/grey or blue/black packs.
Also, you can find the pack for about $50 from motocross places online if you search around. Although, that's only if you can't deal with red.