I am not a huge fan of scrolling through the project browser to get to the sheet that I want to open, or to create a specific family. Currently, I have assigned the key "3 [Enter]" to open 3d view as it is the only one that is assignable. My idea is to be able to right click in the project browser for, say, level 1 floor plan and assign it to the key "1 [Enter]" . This could work for MEP as well to assign, for example, level 1 electrical plan to "E1".
Also, the ability to assign shortcut keys to specific families in the same way would be amazing: "TL" to create your standard toilet, "FR" to create your standard Fridge, etc etc...
I know there are tabs at the top to switch between views, but I prefer the use of keys as much as possible, as I am sure many others do as well.