To answer the original question. Yes it does work. You do however need to modify its shell so that the curbed parts are removed (not to hard actually, you take the top half off and simply brake them off, just put tape over the exposed eletronics so that you don't accidentally short it out). It will then allow the use of a DS or DS lite.
I did this my self and it works. The only downside is that it wasn't physically designed for the DS or the GBA SP, so the little stand will be useless if you use this with a DS or GBA SP. Even with the DS, this still requires that you insert a GBA cartridge into it. On the plus side, the stand works great for my digital camera (since the screw in port is the same size and such) so I didn't have to just toss it in the trash.
Now if someone were to make a DS homebrew app that can boot the tuner, now that would be awesome! It still shows up on the DS when a GBA cartride isn't put in (it shows up as a DS option pak), so it may be possible for DS homebrew apps to access the GBA tuner much like it can with the opera expansion pack and USB linkers and such, so I don't see why it can do the same with this.
As for the official tuner in Japan, it won't work here in the USA since the tuner only works with Japan's DTV system which is different then the ATSC standard. So as of now, we have to wait for Nintendo to port it to the US, which at the moment wouldn't be difficult since changing it to work with ATSC DTV would require minimal hardware changes/software changes.