IF the iPad's sole function, was to play video, then 16:9 would be perfect.4:3 is an old and dated aspect ratio, going back 10+ years to old CRT monitors and tube television sets.
16:10 would be far superior for movies, tv shows and other video content, especially since basically everything now is either 16x9 or 16x10.
For gaming, this isnt even debatable.
For reading, a huge majority of books were all much taller than wide on a single page, and this is especially true with newspapers.
4:3 may work for you. The reality is, its gotta go.
Personally, I don't care for tablets, I think theyre all useless toys that fail miserably to replace my laptop. But if I was going to get any one of them, it'd be either a playbook (i like its size and aspect ratio, as well as it is quite fast) or an Asus Transformer... and I'd probably go with a Transformer seeing how much more there is available on Android as well as the ability to root and flash the device with a custom rom.
Fortunately, Apple wasn't stupid enough to do that. 16:9 or 16:10 works great for landscape video, but sucks for everything else.