Our rule of thumb:
Anything >20 years old, wait until the temp gauge needle starts to move before driving, watch the gauges and absolutely do not flog it until all fluids are up to temp (esp gearbox!). I'm proud of my shop guys, they've not seriously damaged anything yet. (I have, but you know, it's my stuff, so...)
Newer exotic cars wait 30 seconds, don't flog it until fluids are up to temp (doesn't take long).
Modern non-exotics just wait 30 seconds, it's (pretty)...