I agree wholeheartedly. Especially when most of the work I do is on a remote server anyway, so I'm already in tmux. I still use i3wm on older laptops just for the battery life gains, but 95% of what I do is Firefox + Terminal emulator, and alt-tab is just as fast. My main workstation is just gnome and it's fine.
(Sidenote: is there any sort of linux libvte-based terminal emulator that has tmux integration a-la iTerm2? For when I do use i3, it would be really nice if I could spawn a new terminal on a remote server, attaching through an existing tmux session.)