[citation][nom]twelch82[/nom]I think it will dry up as quickly as it started. MS at least is trying to engineer their tablets around pen use, although I would argue they could still do much more. That's the only way it makes reasonable sense.[/citation]
What does it matter, neither is really a negative. They both do the same thing. My wifes iPad displays books. My ASUS Transformer Prime displays books. The human eye is not conditioned to look at books in any specific format, we have conditioned it to read left to right, top to bottom. Most books on the market are not a perfect 1.33 ratio so your argument doesn't make any sense.
I think it likely came down to video format, back in 2005-2006 when the ipad was being designed the 4:3 screen shape was still a common format for video. It is in the last few years that it has really finally started to shift to widescreen designs across the board (laptops, TV's, etc). So it was likely timing, and it could have just been that Jobs liked it more square than rectangle for all we know.
At the end of the day, they both get the job done.