Actually the iBook and Cube design were quite good. Still have my Graphite iBook and works great - and the design was great for it's time. As for the cube, the only real downside was the cost at release. I purchased one off ebay a few years ago for a great price and it works like a champ.
I'm an Apple person since the old Apple II days. However, being an IT professional, I had to try all the other flavors of tablets. Apple just gets it. No one else understands the tablet metaphor any better than our friends in Cupertino.