Android designers have explained that they moved away from tabs at the bottom of the screen in 4.0 because with both the navigation bar & another set of controls one of top of the other, users were just making way too many input errors. (I don't have the source handy, sorry)

My palm already hits the button in the bottom-right hand corner all the time in certain apps with tabs, like the twitter app.

I really wish they'd get rid of that bottom tab bar and shove them under a hamburger button even though that's supposedly bad.

I got my first iPhone a while ago (a non-plus iPhone 6) and I've found the top widgets very inconvenient to access. Especially the top-left corner which is awkward even when using the phone with both hands. I've found myself arranging the home screen icons so that the most often used apps are on the bottom row (other than the four in the dock.)

That's the paradigm of WP7/WP8 -- and now they're changing it. Sad.

Wasn't the paradigm swiping between columns? That didn't work when there was more than a few columns.

What I had in mind was just relocating the toolbar to the bottom.