I may be missing your point, but if you enjoyed the iTerm hotkey feature on OSX you should take a look at Guake[0] which is available on most linux distros.
I will miss iTerm as well, but I'm not worried. I feel fairly secure in the knowledge that there's lots of terminal goodies in the Linux userland that do the same things iTerm does.
WSL for Windows with Ubuntu works... okay. I think they're totally on the right track, but it's still not smooth. I get terminal emulation problems a lot, and the weird display of the filesystem and the file corruption issues plague me.
I think the thing that most attracted me to the Mac ecosystem (for a long time) was the underlying shell (I do mainly data science, security and shell / sysadmin style work). Now that Windows is headed in this direction...
For all of these - I really wish for a faster video card in all of them. I like to run two P2715Q Dell 4k monitors for my work (thinking about the newer 34" ones), and all of these machines lag somewhat with that. (No, I haven't tried the EGPU for the Mac yet).
I may be missing your point, but if you enjoyed the iTerm hotkey feature on OSX you should take a look at Guake[0] which is available on most linux distros.
[0] http://guake-project.org/