Originally Posted by nebulous50
The DS certainly doesn't have the PS interoperability at the moment. The only way that I know to play video files and music - but not streamed - is via homebrew applications, there may be official ones out there but this is the most convenient and cheapest way.
There is forthcoming Wii/DS cooperation functionality in the form of a Pokemon title coming to the Wii shortly, I believe.
Nintendo have actually promised there will be more, much more of this functionality in the future but when is anyones guess.
As for buying a DS - they are just outstanding fun when you get into them. The touchscreen will hook you in, even moreso than the Wii is doing at the minute anyway. Buy it just for that and see what happens.