I've had a set of the 35's for about a year now. I only have about 2,000 highway miles on them (if that) because the truck is trail only, but so far I'm pretty happy with them. I went through two sets of BFG mud-terrains before the MT/R's and I think the MT/R's are a better all around tire. The tread compound is softer than the BFGs so they definitely hook up better on hard surfaces (rocks, dry dirt, asphalt, etc..). The sidewall tread also seems to help in ruts and protects the tire, I always had trouble with the BFGs getting the sidewalls chewed up but these don't show any signs of that after a dozen or so trailrides.
Two other guys in our club have them (33's and 31's) and are both happy with them.
As far as being worth the extra money, that's hard to say. I have some connections so I got mine actually cheaper than what the BFG's would cost, if I would have had to pay full price I don't know if I would have gotten them. They are good tires, but they are a little pricey.