In reply to wildernesschris:
I've crossed it at Geldie Lodge as late as November and as early as March. Just kept boots on and soon warmed up after that. That's a wee bit upstream from where I think you're intending to cross if you're going Lairig Ghru/Glen Tilt. I've also crossed where I think you're going in the summer months with no problem.
As far as the detour is concerned I have walked along both sides and there is no particular problem on the S side; N side of course is Land Rover track. Can't say how long it would take you but I'd allow at least a couple of hours.
Of course it's all very dependent on conditions at the time and you may have no option other than to detour.