I have an 09 Renegade 800-X and I have put around 1300 miles on it without any mechanical problems. The biggest thing I would suggest, if the previous owner did not do it, is the frame mod. In a nutshell, it entails this: on the rear of the center frame rail that runs underneath the entire length of the quad, there is a rectangular shaped plate that is welded along the top, bottom and both side. You use a torch, sawzall or whatever to cut 3 of the 4 welds so you can bend the plate out of the way. You then use something to fill that hollow tube to protect it from getting bent when you hit stuff with the bottom of your quad.
Different items have been used over the years and who knows what is best. People originally took 3 pieces of 1.5 inch square tube, welded them together and slid them in there. But, steel is heavy so folks are using different items now. There is one company that is actually making a nice aluminum piece to slide in. Go look at this
post for detailed pics towards the bottom. That one is from here
and is gonna run you $99 plus shipping.
When I did mine, I actually used a product called UHMW which is like a solid PVC material. I ordered it online and got it for a great price. I paid $44 a stick for it cut to the exact size I needed and shipped. Here's
where I got it.
All that being said, when I did my frame mod, the ATR product was not out to my knowledge. Who is to say which is the best way to go. If you're just looking at price, the UHMW would be the right track. However, the ATR unit is very well made and obviously made for an exact fit.
I hope that helps a little.