As Micael LaFleur says:
"I think the MB spec is 'no less than .7 bar' at idle. Typical is 1.25 to 1.75 bar at idle. Personally, I would not like to see it less that 1 bar."
Not to put too fine a point on it but I think it really depends on the engine, ambient temp, and choice of oil. My owner's manual says:
"The oil pressure at idle speed may drop to 4.4 psi (0.3 bar) if the engine is at operating temperature. This will not jeopardize its operational reliability.
Pressure must, however, rise immediately upon acceleration."
Mine always used to run pressures around 0.5 bar in summer in stop and go traffic (before I switched to Mobil 1), and I got the car with only 25,000 miles on the clock so I'm pretty sure it was in good mechanical condition then, and now, for that matter.
I think one of the reasons the engineers removed the oil pressure gauge in newer models was to prevent us obsessive types (and I include myself in that group) from getting too hung up on numbers . . .
My manual says to check oil level 5 minutes after shutting down the engine, which implies it should be checked warm. In general, the ideal level is halfway between the two marks. If it's on the high side, my engine (at least) will tend to somehow use it up until it hits midpoint and then stay there. If I just fill it to the halfway mark from the getgo, it'll stay there for the entire oil change interval.