This is why I love message boards - honest opinions!
I agree with you, pdf's are viewable by many users on many different platforms. And yes, that is one of the great things about the pdf format.
However, when it comes down to publishing
e-books..the format is great... many features etc BUT try to make money selling your e-book. (no debate you can make money but I wonder how many sales are lost because of copying? )
Sure you can rely on the honesty of users or pay Adobe royalties (webbuy) for every sale.
As far as the windows platform (no debate of which is best - mac , unix, linux etc) - the fact is: the windows market is by far the biggest.