@EDinburghCycleCam: Au contraire, it's in exactly the right place to catch left-turning drivers who can't be bothered to wait for the left turn lane to start when there's a tailback at the lights. See also Burdiehouse Road northbound at Kaimes crossroads, and Gorgie Road westbound at Chesser Avenue.
Whether it will actually help to improve the flow of traffic there I don't know, not being a regular user of that junction (and certainly not during the operational hours of the bus lane). I'd have thought that it can't hurt as measure to keep pushy left-turners away from cyclists in the bus lane (at peak times, anyway - which are the times when pushy/frustrated/selfish drivers are slightly more commonly to be encountered).
What it might also do is make life easier for motor vehicle users wanting turn left legally, who find themselves blocked by drivers using the bus lane illegally - either queuing, or steaming down their inside at a wholly inappropriate rate of knots (because, of course, if you're using the bus lane illegally then you should make sure that you spend as little time as possible in it, which means that it's quite OK to drive at excessive speed in order to do so). Depending on the sequence of the lights, blocked left-turners can then end up impeding the flow of traffic wanting to go straight on, through no fault of their own.