I tired to watch a few TV shows on my ipod a few weeks ago while on a flight. After about 5 minutes I had such a screaming headache that I could not watch anymore - so I put some soothing AC/DC on.
In theory I like the concept - but in execution it's just not right.. yet.
Podcasts of my favorite radio shows are perfect for flights however...
and they occupy the majority of my ipods memory.