I did a LOT of research before buying this. There are SO many options at so many price levels, and I needed something within my budget but that would still do the job. Overall, the unit works great, and I don't think the rig is trash like the other reviewer stated. I didn't really need the rig because I already had a good rig, I just needed the motorized portion for zoom and focus control. The rig was a bonus, and I actually like the feel of the rig and how it attaches to my sticks, although I find the front handles where the motorized controllers go to not be comfortable for me to hold for long periods of time, but that's just me. Your mileage may vary.

The motorized units that control focus and zoom can be operated either from the grips that you attach to the rig's handles, or from a control box that attaches to the rear of the rig on the rails. This is handy for a couple of reasons. When you're hand-holding a shot, you can zoom and pull-focus with your thumbs that are already in position where you're holding the grips on the handles. This is VERY handy. Or, if you're rig is on sticks, you can use the controller mounted on the rear, and use one hand to operate the zoom and focus, and the other hand to tilt and pan the camera. I've also used this unit with a steadycam where I had to have both hands to just operate the steadycam, and had an assistant walk alongside holding the grips (not attached to the rig) and perform zoom and focus duties while sharing a look at my onboard monitor. This is ALSO very handy becuase the grips come with a decent amount of expandable cable to allow an assistant to stand and move next to you to pull focus and zoom, while you concentrate on framing the shot.

I've also used this on a jib and crane which is pretty awesome because you can use the rear controller to pull focus and zoom, while operating the jib.

Both the zoom and focus controller will operate at variable speeds which are adjustable by rotating wheels embedded in the controller. The start and end motion is pretty smooth, but will take a little practice to master. Oddly, for me, I found I liked the speed of the focus puller best when used as a zoom, and vice-versa. It's just a matter of switching the cables. I found the focus controller's speed and control more acceptable for zooming since I did more of that than focus pulling.

Another plus of the focus puller is you can set preset focus points, so, if you're moving a shot, and you need to rack focus at specific points along the way, you can set up those points in advance, and a push of a button will change your focus to the place where you set it. This works best of course under controlled and rehearsed conditions where you'll know in advance where a mark is, and how you need to focus. Otherwise, you can just wing focus pulling on the fly. You can also set a max "in" and "out" setting for both the zoom and the focus to prevent you from trying to move either past the ability of your lense. This is great to keep your lense from pulling back too far and exposing your matte-box.

The only downside I experienced was that the motorized unit's wheel that locks into the gear ring that you place on your camera keeps losing its grip. I've tried several time to tighten the position of the wheel unit against the gear and it works fine for a while, then slips out of position. This is a major pain when using the unit with a crane or jib because you have to bring the whole unit down to your level to fix it, and also, it's a pain because it spoils the shot when the gear stutters and won't focus or zoom. I'll keep working with this and update this review if I find a solution, or happen to talk to their tech support to see if there's something I may be doing wrong.

Overall, I'm happy with the unit. The gear slippage is only occasional, so I'm living with it for now, but may need to find that I have to step up to a more expensive unit if this continues to be an issue.

The shoulder rig is total trash, let me get that out of the way right off. The focusing/zooming motors, on the other hand, are phenomenal.

Anyone that had experience with the MR-400 model (that used belts), knows that those motors wear out fast and are harsh on a lens. These motors are quiet, much larger and more robust than the previous MR-400 models, and they work very very well. I bought this shoulder rig specifically for the motors and I have them attached to my Zacuto Scorpion shoulder rig. I'd gladly make the purchase again specifically for the motors.