Personally I think waiting for the operating temp to rise in idle is better for the engine than thrashing the engine when you think the operating temp has been reached i.e. most people wait for the coolant to get to 90, but at that point the engine oil will still only be about 50 degrees.[/quote]
I don't buy that either - water is the coolant, so it has to be colder than the thing it is cooling (it's impossible for it to be hotter). Water also has one of the highest heat capacities going (hence it stays hot for ages) - oil will get up to temperature much faster than water (why its used in oil-filled radiators etc.). If your coolant is at 90 deg C, your engine (and your oil) is going to be hotter than that, not colder?