1) D-matrix reduces damage to 0.5, not 0. Also an irradiated unit receives way less damage if it has D-matrix.
2) You can create a network game with a name like "whatever #x2" or "asdf #x1.5" and the game speed will be x2 or x1.5 times fastest. Any number seems to work. I've been using x3 to practice build orders quickly.
3) You can have "reserve scanners", just build another scan near the real one and put the CC back in its normal place. Later, if you run out of energy, lift the CC and place it on the other scanner, it will have full energy.
4) The 0 key on the numpad shows the opponent's stats.
5) Ctrl-C and Alt-C center the screen on the unit BUT the real important thing here is that it centers on the first unit, so if you select mutas + ovie, using ctrl-c will be easier to go back to the mutas compared to double tapping the group number.
6) You can find out which vessels have energy by casting irradiate on something far away, only the ones with enough energy will move.