I've been experiencing with the Wii channel technology lately. I picked up a few games for the different platforms available and tried them. The ports are really good but I still do not quite understand why the Wii insists on stretching the output if you have a wide-screen television set. Needless to say, these retro titles do not support wide-screen.
The other big question that comes to mind is why is there no Game Boy channel? It seems that Nintendo is no longer actively promoting this platform and with good reason considering the massive success of the DS. It is true that the DS can play Game Boy Advance games and Nintendo may still be protecting revenue there. That being said, the DS is incapable of playing older titles for the original Game Boy(GB) and Game Boy Color(GBC) platforms since it doesn't contain the vintage hardware to run those games.
The GB and GBC platforms have a fantastic software library that I never got to play. Do I really want to pickup Zelda: Oracle of Seasons and a GBC from Ebay? No, no I don't, but I can really see myself purchasing that title virtually on the Wii however.
Now, what about linking? That annoying game technology that Nintendo tried to push on the market as an alternative to online play. The simple answer... just don't support it. The DS doesn't after all. Nintendo was able to use this linking technology to provide some unique gaming experiences but it ultimately failed since most gamers seemed isolated or missing all the required hardware and cables. So again, just don't bother supporting it.
Finally, I would argue that Nintendo is probably losing some real sales here. There seems to be an abundance of GB emulators and illegal software ROMs available on the Internet. A legalized option, at least, would most certainly deter some gamers from getting the setup on their computers.