I am also long on NTDOy (I do not think this is a very easy stock to short, most bashers are SNE longs) here are the negatives that I can think of, you guys have got most of the bullish arguments out of the way.
1. Wii is a fad. I don't believe this and with what 19 million units sold and going strong this sounds unlikely. Still some of the games for the wii like Wii sports and Wii play get old real quick.
2. Inability to increase production to meet demand. The economic situation that this round of consoles is going through is really festinating. You have SNE that priced PS3 to high and had to much supply. You have xbox that has really been pretty good with inventory. Then you NTDOY who could have set the price of the Wii at 300 at least and sold as many units as they have now. How hard is it to increase production. Retool a few factories and start making them. If you need components pay to Retool more factories to make components.
3. Exchange risk. Nintendo gets nearly 75% (my own rough estimates please correct if you have a better number) of sales from outside Japan. So far the strong EURO and Pound have made up for the weak dollar with a little help from stunning sales growth. Once growth slows the effects of translation will become more apparent(probably early 09).
4. Lack of liquidity in the stock. This has been discussed in good detail on this board.
I do have a difference of opinion on one of the bullish points made on this thread. I do not think that we need very much support from 3rd party developers. Sure it would be nice for an EA boxing game that used the wii fit and wemote. Or a Grand Theft Auto that uses the zapper. In the end few if any of these games will be released exclusively for the Wii. I contend that very few people have a Wii and no other system, at least not "hardcore" gamers (I hate that term). I have an xbox 360 for my other games but I will definitely be playing Mario Kart with my friends as soon as it comes out. Ditto for Smash Bros.
Remember still no Donkey Kong title for wii, only one pokemon, none of those brainy games that sell so well for ds, what about a nintendogs? This is why Wii is so important to this company. While DS has likely peaked or at least leveled off, the Wii is still 2 years away from this point. All in all it should be 3 more years before NTDOY has to roll out a new system so for the next year or so R&D should be the lowest in years even as the company rolls out winning software title after title.