If you launch GameGuru with any shortcut that was created by the installer, the Steam client will automatically launch. For me, this is fine, for others, it may not be. I just discovered that if you manually create a shortcut to the GameGuru executable, Steam will not launch! Remember, of course, multiplayer will not be available, however, this may be useful in troubleshooting down the road. I just discovered this by accident, and thought I would share.
EDIT: I now have two Game Guru shortcuts; I just called the second one Non-Steam.
MAME Cab PC: i7 4770@3.4Ghz (passmark 9945), 12GB RAM, Win 8.1/64, GeForce GTX645 (passmark 1898); Shiny new laptop: i7 4800MQ@2.7Ghz (passmark 8586), 16GB RAM, Win 8.1/64, GeForce GTX870M (passmark 3598); Old laptop: i5@2.3Ghz, 8GB RAM, Win 7/64, Intel 3000 graphics