Heathrow Director- I can understand your confusion because of the tone of some of the comments here (e.g. Jammers) This indicates the different levels of compliance with Boeing SOP's by different airlines! FACT- the minimum speed GEAR UP speed that can be flown using STD procedures on a "Classic" 737 (3-4-500) is 170 knots at Flap 10. I am fully aware that flying at 160 will not necessarily cause a crash BUT that is the speed that Boeing say to fly and in my airline that is what we do! The fact that some airlines are much less rigorous in their procedures is their concern but I'm not an aerodynamacist so I stick to the makers manual!
I hope that clears the air!