I am surprised at the sheer volume of responses... I love it when people get excited over such things!!
I will summarize my position on the matter as this...
The location is completely arbitrary to me... left- right- top-bottom... doesn't matter. If someone has some empirical evidence that points to some ergonomic benefit of one over the others then GREAT... go with the science!
The real key is trying to make all movements instinctive... and logical... if you are going to present information... put all of the ones that need player input in the same place! If you need to edit... you go to the same area on the screen as you would to draw up the placed units... or history of moves... or whatever.
By having players know where to get all the tools they need to play the game makes it an easier and more enjoyable experience.
All the other tacit info that is there for the players benefit can be located where ever so long as it is consistent and in fixed locations across games.