I do imagine that movie viewing would be far easier on the PSP, but I don't think that's enough for a sale (especially with the way cell phones are heading). The libraries might differ a bit with their target groups, but I'd not say the DS library is overwhelmingly childish.

However, the reason I got a DS was the same reason I got a Wii, something different. If I want hardcore gaming, I'll go to PC. If my PC for some reason explodes, I could somewhat replace it quickly with a XBox360. Lol, if I need a bluray player, I get a PS3. But since I've got the hardcore under control, I grabbed something on the other end of the spectrum.

Besides, hardcore and deep games don't lend themselves as well to handheld play, unless of course you have a lot of regular downtime in your day (long commutes or something).

I've only managed to handle and play with one PSP outside of a display kiosk, most of my friends have simply passed over the PSP. At the very least, I would further investigate the PSP's hardware problems before recommending a sale.