I'm pretty happy with the R4's MOST of the time. I have a LOT of topsoil and if it isnt dry, the lugs will load up. I solved this buy putting a set of truck chains on it. They are not to aggressive but give just enough more traction for when I am in places I shouldnt be /forums/images/graemlins/grin.gif or there is moisture in the ground.
BTW, the only level ground I own was made that way by machine, I am always on a side hill.
I really like how 90% of the time they float without causing damage or tearing plants out.