I've worn out a pair of these fantastic shoes through daily training. They're better, for me than the model (Musha 5) that replaces them.
The upper on these shoes is really something, like a spike with a "dancing pump" fit giving great feel for the surface.
I've done a lot of hours in this shoe and never once regretted buying them. I got the 5 and they're nice too just not as good on the road or off it.
I think I'll get another pair to replace the Musha 5's when they too wear out.
If you are tossing between these get the 4 the weight loss on the 5 is probably not worth the extra money and as I said these feel better to me.