All of those names have potential, as well as drawbacks...
.jp's are of course Japan, a powerful commerical/capital center.
However, they also cost 8 - 10 times .com's, so make sure the name really is quality, and not overly speculative.
.cn's, we'll see which way the country goes (restrictions/free trade/etc) but they are the "home extension" of such a huge populace that it would be hard to imagine it not being a good play for quality keywords.
Feel free to search the forum for other more involved discussions of these discussions!
-Allan