Well, I guess it would depend on your application and needs. I am not an expert by any stretch, so I will give you my opinion only.
1. I have about 8 acres to cut, of which 6.5 is open field with very minimal obstacles. I have a few pine trees out in the field, but not many.
2. Around the house, garage, driveway, and my kids playground it gets a little tight, with the minimum clearance between obstacles (trees, benches, buildings, timbers) is about 6-7 feet.
3. my ground is relatively flat, especially for the mountains in PA
For those reasons listed, and using it for a total of approximately 14 hours so far, I would say I love it. Here are the reasons
1. The noise factor was reduced substantially. My previous MMM or bellymower made alot of noise. I only hear the RFM banging from bumps. At first I kept looking behind me to make sure it was cutting.
2. I can detach it easily, and I don't have to worry about my MMM getting in the way ever again. When I would get lazy, which seemed to be more often then not, I wouldn't remove the MMM when I was doing FEL work. Now my tractor wasn't a monster, but the MMM would get in the way all the time. On several occasions I had to remove it, including all winter due to it getting caught in snow.
3. I can back it into areas that I could never get my MMM to cut. Saves me some weed wacking time, but I will describe the offset of this later. This is especially useful for under trees that are high enough to cut under, but not high enough to ride under.
Here are the cons (for me):
1. It doesn't cut as close as the mmm would. I could maneuver the tractor around to get within about 2-3 inches of obstacles, then come back and clean things up with the weed wacker. It also is slightly more difficult to maneuver, by which I mean that when I turn around with the tractor I have to take into account that the RFM will swing out behind the tractor for the entire turn. Since it is in a fixed position, a turn creates an arc of mvement, which is difficult to describe. I attempted several times to get the RFM closer to the obstacle (e.g. the 8x8 creosote timbers by my daughters playground), but found that I couldn't get as close as the MMM. This may be newbie driving, or it may be the equipment.
2. When you cut by any ruts or ditches, you have to be careful that the RFM wheels stay on grade and don't slip over. If they do, you kind of saddle bag the RFM, and the weight kind of throws the rear end over a bit.
3. The RFM is behind you as you cut, so you are constantly looking backwards while driving forward to see if it cutting where you want it to. I know some will think I look tooo much, but I get rather obsessive about grass cutting.
Hope I gave you some info in this rambling dissertation. My only regret is that it is 5' instead of 6', for the open field only.