Where did the "hide the toolbar" thingy go on OS X Lion? On OS X Snow Leopard, there was an option to hide the toolbar in many applications, such as 


but I don't have that option on Lion anymore

This isn't MacVim specific issue, I don't see it in Adium and many other applications too. Did the button just disappear? Is there any way to show ita again?
I don't think there's a way to make the toolbar capsule widget thingy show up again.

However, if you want to hide the toolbar, you can right-click on the empty toolbar area and choose the "Hide Toolbar" option:



You can also go to the View menu and choose "Hide Toolbar" from there.  It may also have a keyboard shortcut of cmd-opt-t.