Well I have to say, I drove through Haymarket today, and it's still a mess (although I was going west, not east - I avoided going east by cutting over onto the A90 on the return), particularly since I come via Queen St (so have to do a massive detour even just to get to Haymarket). I'd go with those thinking getting in about 1350-1400 is more realistic. They've also started work on the A8 west of Haymarket, which means the road is down to one lane (i.e. no dedicated bus lane available).

I'd agree on cursing the trams if you are late, it's now the standard EDI excuse - they've removed the need entirely to converse with taxi drivers, as all you need to do is mention trams and the drivers will rant until you reach your destination