Basically, the minibuffer is small and at the bottom of the screen.
With a large monitor especially, this means I often need to lean forward to read it. It is also very long - this makes it slower to read. (no line breaks)
The minibuffer is sort like a launcher/error area - so it seems logical that it act more like some combination of quicksilver/growl.
You can make the minibuffer taller by using the function enlarge-window or its keyboard shortcut C-x ^. See is it possible to move the emacs minibuffer to the top of the screen? for some thoughts on how to move the minibuffer itself.
Consider using a standalone minibuffer frame. That saves real estate: no need for a minibuffer in each frame. And it also lets you configure the look and feel separately for the minibuffer. I use a minibuffer frame that extends across my whole screen and is (by default) 2 lines high. The minibuffer can hold any number of lines, BTW.
This is what I use, in case it helps:
