With all the upgrades coming in recently (and hopefully ones in the future) it might help to start categorizing them into drop down menus or something of that ilk, you could also incorporate the ability to buy that whole section in one, making it even quicker. This would help so that when we start making huge money we don't have to scroll, buy and scroll down some more as it's just a tad inconvenient. At least enabling us to use the scroll wheel on the menu would help this, this is a great game though guys, keep up the brilliant work :)
The game needs a LOT of UI work. We're actually talking to some designer friends of ours right now.