I have the Archos 704 wifi and DW has the 504. They're an excellent brand and the quality is top drawer. With the "additional" docking station you can use them as a hard-drive video recorder. With the 704 you can plug your digital camera straight into it and download all of your photos, freeing up your camera's memory card. The 504 needs to be sitting in the docking station to do this. The 704 wifi can also access the internet.
The video quality is near DVD standard, and they will play back onto your TV in full screen mode. You can copy commercial DVDs onto them although you will not be able to play these back onto a TV due to copyright protection. A word of warning: to copy DVDs onto the unit you need to download a "plug-in" that costs about £13.
The playback time is approx 4.5hrs for video and between 15-20hrs music.
They come with a "snazzy" universal plug that allows you to plug into UK, Europe and the US. They're auto voltage switching so no problems with incompatabilities.
Depending on how you compress your films for copying on a 30gig unit you could have up to 30 films.
We're putting on about 10 films each on ours for the trip over to Orlando.
Any more questions, please ask.