If I have multiple sheets open, there is a tab for each one. It's intuitive to me to be able to close a particular document by RMBing on the tab and selecting close. This is how excel works. I've had to learn at least twice now that you have to click the x at the top right corner. I suppose after learning that a few more times, I will remember, but I hope the goal of this tool is to make it intuitive.
I think that Excel is the only app that I use that /requires/ a RMB to close a tab. All my other common tools use the X on the tab, which I find faster, even though I do remember, sort of by instinct, to RMB the Excel tabs.
