I prefer using the keyboard instead of a mouse when at all possible. Right now I can type "cmd-l" on my Mac to bring up the Library pane. I type "na28" and it's at the top of the list, but since the focus isn't on it, I still have to use my mouse to select it. If the focus was on it, I could just hit return to open it. If I could use an arrow key, or perhaps hit return twice, that would be fine too.
Seems like a small thing, but it's something I do multiple times a day.
Note: I'd even pay a subscription fee for this feature :-)