That's very helpful, thank you. I've never bought anything from the U.S. store (other than downloading the worthless Opera channel), so I have nothing to lose. I just want to play Mr. Driller since there is no US/PAL date announced, and the "sceners" almost never dump good Japanese WiiWare games, at least not on the trackers I've seen.
If I have to switch the Shop channel back to U.S. in the future, I'll just rip my purchases to wads--I guess that means the license will be lost, but who cares as long as the content is backed up on my hard drive. There are tons of great Japanese WiiWare games, and I want to play them!