On a BA flight LHR-SIN last year, was met halfway down the airbridge by a BA staff member (female) with accompaning Plod. During our "discussions" about carry-ons (single computer bag, but overweight), about 20 other pax went past laden to the gills. (This is the only time I've tried the "let me through, I'm a gold card holder!" line.)
There is an anomoly here, as handbags and computers don't count in the carry-on weight, but by the time you've put a Notebook, power supply, phone, various cables and a small amount of paperwork in a bag you're well over 6kg.
BTW, I was let on providing I took the notebook out of the bag and carried it separately. The flight was busy but not full.