Haven't had any issues with the rhythmic aspects that make it impossible to listen to the music. Some drummers are better than others of course, and there are really wonderful drummers in Japanese jazz, both of the free and less free variety -- George Otsuka, George Kawaguchi, Motohiko Hino, Masahiko Togashi, Takeshi Inomata, Sabu Toyozumi, Takeo Moriyama, Hiroshi Yamazaki, Shota Koyama... just to name a few from the glory days of Japanese creative music.
The J-Jazz comps are neat. I don't own any but I like the idea of them and the guys assembling these albums are very knowledgable and have incredible collections. The only downside is that the cost of obtaining original full LPs keeps going up, up, and away as more people learn about them.