I use this one (Ameristep Grizzly)

It can be a little cumbersome to get the deer's center of gravity balanced right over the axels, but once you get him positioned nicely and tied in place, it's smooth sailing.

Like Bearklr said - these things are NOT good for going up steep hills, rocky areas, or through thickets. You almost need a semi-level area, like a field or a gas line or an old road bed.

One area I hunt is a legitimate 1.5 mile hike out a National Forest access road (gated shut). The road winds out across the ridge, crosses a couple small draws, but the cart rolls over it like you're pushing a shopping cart. What would normally be a 3+ hour sweatbath, miserable drag can be done in under 30 minutes with the cart - and you'll barely break sweat.

My only complaint is that when you get a full load on it, it tends to get a little top-heavy, and wants to flip over if you get it on a bind. That's really not a problem if you have the deer tied securely to the frame (I use my treestand safety harness and a ratchet strap).