I had a northstar 30 ton for about 5 years. The wedge design works fine. But there is very little room around the wedge when it's retracted into the "log stripper." Bits of wood gets compacted inside and the cylinder can't retract all the way which puts pressure on the bolt connecting the wedge to the ram. It breaks often. Getting the compacted wood out was not easy and often meant having to unbolt the "log stripper" every few cord to clean it.
You can't use a regular hex head bolt because there is no room. You have to use a 7/16" socket head cap screw as the bolt is recessed inside the collar of the splitting head. Eventually the hole in end of the ram gets elongated and the bolt breaks more often since there is more play in the connection.
I'm sure it works fine for someone doing a few cord a year. But I was using it for 15+ and it wasn't holding up. I see that the new splitters have a redesigned setup with more space around the wedge when it's retracted.