Since I have not seen a Mugen cooler since I wrote the review on the Mugen 2, I can tell you a lot has changed since then - some good and some better, but it stills need work in one specific area. The H.P.M.S. of this cooler is super simple, all the way to the point of mounting the cross-bar. I get shipping a wrench at least offers a solution, but let's be honest here, turning a screw 25 to thirty degrees at a turn is almost more torture than it is excitement to be using the cooler. I would have loved it if the bolts were taller than the sides of the cross bar, where you could get closer to 180 degree turns, or better yet, send a screwdriver like the one Noctua includes since the fin body is too close to use a Phillip's #2 screwdriver unless it is exceptionally long.
Beside this oversight in my opinion, the changes to the hardware does make for a much tighter and much more secured cooler than I had with the Mugen 2. I also liked the new design and the way Scythe has created the T-M.A.P.S. system of separating the towers and bending the fins to take better advantage of the air flow. I also like that there is now six pipes again instead of five, and I think the way they are distributed through the cooler body is as good as it gets.
The performance of the Mugen 4 was about average in both of the thermal tests, but I can see easy solutions to increasing performance. The 1400RPM fan sent along with the Mugen 4 is designed more for the silence it offered in the audio result charts, not really for air flow and static pressure that this design needs. While you can easily add another fan, as long as you remember to get more fan mounts too, since only one set is sent with the cooler, you could drop the results about two degrees on both thermal tests. What I would suggest is a fan that is a bit noisier, if you can take it, and grab something with closer to 3.0mmH20 of static pressure, and closer to 90 or 100 CFM numbers. Then you would take this cooler right into the mix with a drop in the results much closer to five degrees, and maybe six or seven with a pair of different fans. As it is shipped, I am okay with it since the fan is so quiet during idle and not loud at all when loaded. Seeing average thermal results is always a bit disappointing, as I am looking for innovative chart toppers, and the Mugen 4 is nice, but it is not a chart topper by any means.
Since the Mugen 4 is only currently available in Japan by the looks, I can't really tell you to run out and buy this cooler at this moment. With all things considered, specifically price versus performance, things look much brighter. The pair of coolers on either side of the Mugen 4 in the overclocked thermal results are near $80 cooling solutions, and the Mugen 4 is only going to sell at $50, and I really like that.
What sort of kicks the Mugen in its grapes is that the Thermaltake NiC C5 is priced the same, gets much better results, even if much louder, but in my opinion is a much better all around solution. If you are looking for something that is affordable, quiet, and will handle most anything you throw at it, the Scythe Mugen 4 will do all of those things without question. To me it all comes down to if you want to deal with the mounting system, when just about any other cooler is much easier to install.