We have one and it is around 8 years old now. Have not had one problem with it and works great for our application. What were you looking to do with it? We use it mostly for residental driveway tearout (used on a Cat 262). Hands down, it is better than a hydraulic hammer for anything under 6" thick material. The surface contact area breaks it better and covers ground faster than a hydraulic hammer. Depends on the circumstances above 6" thick. The video they sent us when we were first looking showed them doing a good job with 11" bridge decking removal so it is not totally limited.
As long as you keep your pins lubed, you should be fine. We have not had one problem related to the unit or the machine as a result of the unit for the entire time we have had it. The only maintenance on the unit is grease. There is not much else to it except plastic cushion spacers (not bad) and springs to absorb the load so it all does not travel into the machine. What were you looking at putting it on?
As far as performance, it has been a great investment. It takes just a little time to get used to though. It is mostly a timing thing when you are trying to cover sq. ft. It puts a little stress on the machine if your timing is off and you try to lift it before it has hit something on the down swing. Also if you go down to far, it puts stress on the unit but will stand the machine up like a fixed bucket does. When you get used to it though, and on 4" driveway, you can cover ground. Depending on how small you want it broke up and the condition of the stuff you are removing, 10 mins. or less will break up enough to fill a tandem truck. It also has some advantages when reaching into a spot where you would not normally be able to with a hyd. hammer. I start and work my way out hammering till i get enought to fill a truck (single axle in our case) then pick a control joint to start on and hammer it till you can get in with a bucket to start picking it up. The more you hammer it the smaller it gets. Usually on the joint you can hammer it the the point you hammer small pieces down so you have a hole to start scooping. We also use a Yukon Jackbucket besides a regular heavy duty bucket with teeth for our removal. On the 4" stuff, a hyd. hammer just punches through making a hole instead of breaking the slab. The area of the head on the powersledge spreads the blow out over a bigger area more often cracking it but can still punch through in extremely bad concrete. Plus by not punching through you can constantly keep moving while hammering, where as on the hyd. hammer, you have to stop and apply the hammering before moving.
The only possible down fall is that, depending on what machine you are going to use it on, fatigue could be an issue. We first started with it on a Mustang 2070 skid loader with t-bar and foot controls. The way the unit works is by tipping the bucket up and down. On the foot controls, you get very tired quickly. Because of this unit is the reason why we went to Cat for our next machine. At the time Cat was the only one (or one of) that you can drive with one hand (t-bar equivalent) and run the bucket controls with the other. The way we got around it at the time was to weld on a bracket with threads onto the side of the pedal that operated the bucket controls and when we wanted to use the hammer we could use either our feet or screw in a pipe into the threads and run the pedal with your arm while your foot rested. However, the constant pumping of the arm also gets tiring, but switching back and forth allowed for non stop work. Most times though, we never ran it for more than about 20 minutes because we wanted to get to loading some. On the Cat and their controls, you can go as long as you can stand to take it (minimum fatigue). I sort of remember too, when we were looking at these, they were built and designed for backhoes and mini-ex and the skid loader application was and after thought and not well tested. We have tested and works great. We also able to carry all of it on our Towmaster T-16 DDB trailer too (Power Sledge sideways on the front of the trailer, Yukon Jackbucket next to that, and the machine on a 20' deck and beavertail as planned). Hope this helps. Any more questions, ask away.
