If the sales are poor, it isn't for any of the above reasons. It's because of price. The DS moved in record numbers not because of the games, but because the dual-screens, touchscreen, and wireless were perceived to have a much higher value than the $150 cost. There is potential inherent in the technology, and even though people might not be consciously aware that they are making a decision like this, it happens. The PSP's value is very close to the $250 they are charging, which is probably why they aren't moving as fast. At $199, they'll probably move far faster, which is why every analyst worth their salt is predicting a holiday price drop.
There is also the idea that $199 is the "mass-market" price for any electronic gadget, and Nintendo came in under, Sony came in over. The reason is likely because Nintendo is aiming for families and casual gamers, Sony is aiming (for the time being, anyway) for the early adopters for whom the price delta rises to roughly $399. The numbers of the sales currently support the theory as well.
So this begs the question ... does Sony know what they're doing? I'd have to say yes. It's classic Sony (and Apple) pricing strategy, price the device ever so slightly out of the price range for the mass-market, but well under the early-adopter market. That will ensure brisk (but not overwhelming) sales at launch, generate the buzz necessary to create mass-market demand, and then drop the price in time for a major buying season and capitalize on the demand.