Keef:
Missing a couple of important checks there. My mnemonic is:
SPLITT
S trobes(if fitted): ON
P itot Heat: ON
L anding Light: ON
I nstruments: DI, Compass and Runway direction all agree
T ransponder: ON with Mode C
T ime: Note for PLOG purposes (and cost if appropriate)
In the commercial world I believe it is common practice for the NAV lights to be turned on whenever there is power to the aircraft systems. This can alert ground staff to the fact that control surfaces etc might move without warning. It seems good practice to turn the nav lights on at all times unless the issues already given regarding auto-dimming of instruments etc. are relevant. This can also be a help with the Piper types whose strobes and anti-coll are not independently switchable. Nav lights are preferable to blazing strobes when taxiing.
As for the 'when it's dark enough', that is a bit like the people who drive round in the dusk with no lights on because they can see where they are going. Maybe they can, but they can't be seen so easily!!
Fully concur with the 'no strobes at the hold' concept. Basic good airmanship, that. Look at most airliners and you will only see the HI strobes coming on as they enter the runway.