(Observation) Secondlife truly never sleeps.
Anyways, among the commercial parts of the sims beyond the adverts that caught my eye is the subtle difference in artistic stylings. Take any old US/EU skin creator, many of these folks focus on either extreme realism or some form of extreme pseudo-mannerism (stark lighting and rich color palettes). But the Japanese skin creators by comparison tend toward subtle shading and almost pastel color palettes. It's not that I their style is superior, but that it's markedly different. Even some of their clothes focus on more traditional trends among Japanese subcultures, but with a stricter adherence to their historical originas such as the Lolita dresses and the like, which look more like Edwardian/Victorian period pieces than Goth/Scenester clothing.
And my final observation about the Japanese sims is this: they're growing. As much as they don't look massive compared to the cluster of sims that some companies and individuals own in SL, many of these sims owned by Japanese firms and individuals are clearly building up and they're quite organized. Organized in the sense that there is strict planning in plot arrangement (similar to RL city street grid layout) and each plot that isn't sold is demarcated with a sale sign with all the important data laid out (of course in Kanji and the other non-english languages [but with the numerals that we all use today]). I suspect if LL gets their act together on sim management (and possibly doing the same for the Linden Exchange), they could take full advantage of this clear growth in the Grid, rather than just spinning their wheels.