Round power connectors are crap. The jacks stretch and stop making proper contact in no time. Apple used to use them back in the PowerBook days, and on the PB 145, I broke at least three cables and at least two or three jacks on the back of the device over the course of three or four years.
What in the everloving god do you DO to your laptops? I just polled the guys around me and in a collective 30 years spanning thousands and thousands of machines we came up with TWO machines that needed repair due to power port problems.