Up until recently, Archos has always been at the forefront of portable video players. IMO, they always made the best stuff, even better than their competitors such as Cowon and Creative.
Lately the iPod Touch has eaten a little of their lunch, because the form factor is so darn appealing. Still, if you want to watch
and store a lot of video on the go, Archos is probably your best bet as far as large-screen hard disk portables go.
HOWEVER, I've had a lot of experience with their products (I believe I've had one from every other generation), and there's always something wrong with them:
Jukebox Recorder - just bad software, and the mic recording line went the entire length of the device right past the hard disk, adding whine to every recording. Stupid. Still, it was pretty much the first MP3 player I saw that could record audio.
AV340 - while amazing in its day for having a huge screen (which wowed everyone I showed it to), it was a heavy brick with abysmal battery life, and the software wasn't that great on this one either.
604 WiFi - The best player from Archos that I've owned. The software was decent, the form factor was solid (brushed aluminum!), and the screen was beautiful. But it had two speed issues: slow processor and slow (and poor) web rendering.
Some people have other lesser quibbles with Archos, like their tendency to make you purchase certain codec packs, but the ones I've mentioned were the serious product-related issues. I only mention them so that you'll get a sense of the kind of hardware they make. It's great stuff, and I always root for them, but it always has one or two big problems.
Sadly, I've heard that the processor in the new models also suffers from poor performance. Be sure to read reviews before you commit.