Don't you mind the black bars that sometimes take more than 50% of the screen?

I found (after a lot of trial and error) that I enjoy videos most when they're full screen. The tablet's screen is small enough, so why not use all of it?
I also found that you can safely crop most widescreen productions to 16:9 without loosing anything important. They seem to shoot films so that they look good on a 16:9 tv screen. On a screen as small as the tablet's, the difference between 16:9 and 15:9 is only a few pixels... So I cut off the left and right part and use 15:9, full screen.

4:3 is different. You cannot easily cut off top and bottom to make it fit our screens, this will always cut people's faces in close-ups. Also, stretching the image is too extreme, it doesn't look good. But a combination of both works. If I cut off only a little to achieve 14:9 it is hardly more than what TV productions calculate for overscan. The remaining difference - 14:9 to 15:9 - can be achieved by a little stretching..... still noticable, but by far not as bad as the 4:3=>15:9 strech, and very acceptable.

I find it very interesting to see in this poll that a lot of people don't seem to bother and simply take the source material without changes. I would have bet it was different.