$ update-alternatives --display x-terminal-emulator
x-terminal-emulator - auto mode
link currently points to /usr/bin/guake
/usr/bin/gnome-terminal.wrapper - priority 40
slave x-terminal-emulator.1.gz: /usr/share/man/man1/gnome-terminal.1.gz
/usr/bin/guake - priority 50
slave x-terminal-emulator.1.gz: /usr/share/man/man1/guake.1.gz
/usr/bin/koi8rxterm - priority 20
slave x-terminal-emulator.1.gz: /usr/share/man/man1/koi8rxterm.1.gz
/usr/bin/lxterm - priority 30
slave x-terminal-emulator.1.gz: /usr/share/man/man1/lxterm.1.gz
/usr/bin/uxterm - priority 20
slave x-terminal-emulator.1.gz: /usr/share/man/man1/uxterm.1.gz
/usr/bin/xterm - priority 20
slave x-terminal-emulator.1.gz: /usr/share/man/man1/xterm.1.gz
Current 'best' version is '/usr/bin/guake'.
that guake got set to the best version for me because somehow it got a priority of 50, winning out over gnome-terminal.wrapper. doing a --config allowed me to specify gnome-terminal.wrapper again, and Ctrl-Alt-t starting working as expected. Could be that this is caused for some by something during the upgrade to Vivid causing priorities to shift, and something unexpected like guake to be what actually happens when Ctrl-Alt-t is pressed.
As an added data point, I found in running
$ update-alternatives --display x-terminal-emulator gnome-terminal. wrapper - priority 40 emulator. 1.gz: /usr/share/ man/man1/ gnome-terminal. 1.gz emulator. 1.gz: /usr/share/ man/man1/ guake.1. gz emulator. 1.gz: /usr/share/ man/man1/ koi8rxterm. 1.gz emulator. 1.gz: /usr/share/ man/man1/ lxterm. 1.gz emulator. 1.gz: /usr/share/ man/man1/ uxterm. 1.gz emulator. 1.gz: /usr/share/ man/man1/ xterm.1. gz
x-terminal-emulator - auto mode
link currently points to /usr/bin/guake
/usr/bin/
slave x-terminal-
/usr/bin/guake - priority 50
slave x-terminal-
/usr/bin/koi8rxterm - priority 20
slave x-terminal-
/usr/bin/lxterm - priority 30
slave x-terminal-
/usr/bin/uxterm - priority 20
slave x-terminal-
/usr/bin/xterm - priority 20
slave x-terminal-
Current 'best' version is '/usr/bin/guake'.
that guake got set to the best version for me because somehow it got a priority of 50, winning out over gnome-terminal. wrapper. doing a --config allowed me to specify gnome-terminal. wrapper again, and Ctrl-Alt-t starting working as expected. Could be that this is caused for some by something during the upgrade to Vivid causing priorities to shift, and something unexpected like guake to be what actually happens when Ctrl-Alt-t is pressed.