One nice property of the previous tabs behaviour was that you could close several tabs by hovering a close button and click - the closed tab would be replaced by another with the close button at the exact same place, so you could just go on clicking to close several. With the new wide tabs this is no longer possible.

There was some browser that had wide tabs before, I think it was chrome, and it handled this in a very elegant way IMO: it delayed adjusting tab sizes to the newly available space a bit, while you had the mouse hovering the tabs bar, so you could do the several clicks thing. The GNOME Shell overview uses a similar strategy: it won't rearrange the windows right after you close one, so you can still use your spatial sense to select a window or to close more. I think delaying the rearrangement of tabs would rock.