Huh?
-Line spacing (and spacing in general) is controlled by the cozy/comfortable/compact options in the settings drop-down (the gear in the top right).
- Line spacing - run both versions in different tabs on the same browser and count the lines if you can and find the difference.
-Ctrl+clicking opens emails in a new tab just fine. As a Slashdot grumpy old man, I'd hope you know your shortcut-fu!
- Ctrl+clicking is more effort than mouse-over and right click, no other movement is needed on keyboard. As you may notice, to Ctrl+click you need both hands. Mouse-over right-click only one, therefore quicker. Any extra movement on a computer is repeated zillion times and one movement less is a zillion time less repetive movement.
Many people working on computers have neck/shoulder/upper back issues from repeated unnatural use of their bodies. Mouse-shoulder higher, trapezius assymmetric, tighter on mouse-side etc.
-"Mailboxes"? I assume you mean labels? You can select which ones show without having to click on "More" by going in the "Labels" settings page. There are a lot of controls there, even.
With label selections on html, there is one scrollbar, on the current, there is a 2nd, the process to select a label is more complex and jumpy - second scrollbar, new orientation, point mouse on 2. scrollbar, then reorient. The interface is in control, the user has to follow. With one scrollbar, the user controls more.
I feel like people, when presented with a new interface, never try to even look at it before balking off. Just a bit of actually using the interface and trying its various features can be extremely beneficial and takes only a few minutes.
Yawn....