Curved tank cover means you're buying a shelf...

[Cjccmc]

.... so all the stuff that would have been on top now has a stable place to go?

That's what I discovered after buying my last new toilet that had a shapely and slippery curved top. The Kleenex holder, wife's flower vase, etc. all go plop during the night and fall behind the bowl where the dust bunnies romp. A month later I'm mounting a shelf to the wall.

Next toilet purchase I'll be looking for a shape inspired by the Bonneville Salt Flats

 

[Stuff]

I agree. Worse is the ones that have buttons on top - in the center which is the only place you could possible balance a tissue box.