Tabs get inefficient as soon as you have more than 10 tabs opened. The project manager is better, but it can take you some time to find your file when you have hundreds of them. And both methods make you use the mouse, which is good some times, but not so much others.
The observation that 'inspired' this expert is that you are normally working on the 3-4 last files you accessed. So, this gives you a very fast way to switch between them. Just press Alt-Ctrl-Tab, keep pressing Tab without releasing Alt-Ctrl, and you can select the icon of the file you want to work with. It behaves similar to Alt-Tab on windows, it does not just switch between tabs (like ctrl-tab, or Alt-Tab on win3.1), it shows the icons of the files and lets you choose the one you want. Icons are different for different file types, and files from other projects are shown on black and white.
Bookmars are supported too. You can press '1' to '5' while not releasing Alt-Ctrl, and later you can access that file (even if it is not opened) by pressing Alt-1...Alt-5 Bookmarks are persistent when you close the IDE, so you can use them to mark very used units.