[slmbrhrt]

19 is too many. I use one: NERDTree, and I bind Leader-n to NERTTreeToggle. It's invaluable to me.

[jh3]

I recently switched to Command-T. For me it is faster than NERDTree, especially if you know what file you need to open.

For example: Leader-t, type several characters, enter is a way faster navigating through file hierarchy, in my opinion.