Have mixed luck with mine!
My friends had a number of homemade carts for use in the local WMA's that don't allow ATV use. Rules are that game be removed whole, and they frown on field dressing. I found a moped wheel/tire assm. in a motorcycle junkyard for $25. Light weight, equiped with a drum brake, and a molded "mag wheel" the plan was to fabricate a single wheeled cart for the ages.
Two-weeks later at a sporting goods closeout sale, I found a "MULE" ($75)with an aluminum frame and a 20" bicycle tire. At 12 lbs. you can tote the unit in broke down, assmble and "wheel out" your game alone. Larger deer (over 150#) are a handfull and usually require a partner to assist over logs, dips, mud holes, and crossings. Tire has gone flat, on 2 occations. I put some "green slime" and have had little trouble since. I have used the mule to transport a pop-up blind, and a ladder stand over flat/muddy ground deep in the WMA to escape the hoards. I think one could role a dressed mule deer or half a cow elk in the right conditions. No brakes would make down hills an adventure. In the sage flats it might shorten recovery time on a speed goat, muley, whitetail recovery operation. In the "dark timber" packing out an elk....I think it would be better to pack quarters on a quality frame or pack. The blowdowns would make any advantage with the cart more trouble then it would be worth.