I have the Kunz MR55B Rough Cut Mower. I pull it with a Honda Rincon 680cc ATV, which has PLENTY of power to pull the Kunz mower (the mower's big wheels roll easily on gravel - I block a wheel to make sure it doesn't start rolling unexpectedly - for safety). Actually, the very first time I used it I hadn't move the ATV to the property yet and pulled it using my Chevy Tahoe - that must have been quite a sight. I couldn't see it in the rear view mirrors so my kids were in the back telling if I was too far right or left. I have several acres of unused pastures that eventually will beome horse pasture (in a different state - when I retire - which is why I can't use my JD 3320 to mow). Since I bought the property in 2009 and subsequently bought the Kunz mower I've used it to mow the pastures a several times per year to prevent growth of trees and brush. Sometimes the field is 3+ feet tall. The mower is a beast - built more like heavy agricultural equipment sold at a tractor supplier than backyard equipment sold at a big box store.
Kunz helped me select the model. Originally I planned to buy the Kohler engine, but Kunz recommended the Briggs & Stratton engine. They said that the Kohler was intended for very heavy commercial use and that the B&S engine would do me very well. Indeed they were correct. It has starts well and has plenty of power. I have no problems with post-winter startup too (I religiously use fresh Stabilize gas - keeping it less than 1 year old). The Kunz 23 hp B&S INTEK engine is VERY similar to the 20 hp B&S engine in my John Deere 125 riding mower (which is also stunningly reliable). One more small thing - the Kunz mower has a fairly large 3+ gallon fuel tank which I appreciate. There is nothing worse than having to stop in the middle of mowing to add fuel. Oh, and for changing oil the engine has a simple hose that drops down for draining - makes it real easy to do.
I actually picked up the mower from where Kunz manufactures the mowers and they gave me a tour of their facility. Its a typical small business that is family run. They take it seriously and are very proud of their product. They specifically told me that their mowers are designed for steep ground - they use a higher end battery that can better tolerate extreme angles and bouncing.
I was a little worried at first that the mower blades were manually engaged (my tractors are all electrically engaged) and that there is no on-atv control, but this has been a non-issue. I engage the blades at lower RPM and it seems smooth. I simply engage the blades, climb on the ATV, mow, hop off the ATV, disengage the blades, and lower the RPM to give the engine time to cool down. Its really pretty simple and straight forward.
The other post that mentions turning space and backing up ... I have backed mine up with the ATV - it works but the hitch connection is clunky (built to withstand tilting) and I have to do it slowly. It turns as sharp as I can turn the ATV - it can pivot completely in place when hand moved, so the ATV is really the limiting factor for me. Still the mower is big. Also, as I mow near my pole barn I have to be real careful not to it the building - its not nearly as easy to be accurate as with the belly mower on my SCUT.
I did have one odd thing happen a few years back. I was mowing with the mower off to one side (it can be set for right, left, or behind the ATV) to better cut raspberries and somehow a vine or something apparently caught just right on the oil dipstick to twist it, pull it out, and drop it on the top of the mower deck. There was no damage but some oil splashed on the top of the mower and deck. I was kind of surprised so I just cooled it down and cleaned off the oil with paper towels. In the end there wasn't even enough oil loss to notice with the dipstick. I was pulling it through brush and tree limbs that I wouldn't be able to walk through - I was kind of busting through them (maybe lucky I didn't bend the dipstick tube!!), so I wasn't surprised and it hasn't happened again, so I don't worry about it.
If you have any specific questions just ask. Happy to answer them if I can. Don't hesitate to call Kunz if you have questions for them. They were happy to talk to me when I called them.