I lean towards pullet, but the posture makes me think roo. Probably have to wait until either it crows or lays an egg. I would have thought that if it were a boy, you would be hearing the first attempts. Has it's voice changed - from peep peep to Bawk bawk? If so and there still is no crowing and you don't have another roo, then I would say girl for sure.
I'm thinking pullet as well. My Austrolorp pullet was a big girl & I thought she was gonna be a roo too, but she's all girl. The comb says pullet to me.
I feel silly, but today I'm calling my feathered beast a pullet. I took him/her/it out of the coop today and just don't see any pointy hackle or saddle feathers. Its legs aren't really any thicker than the other chicks' legs. I'm prepared to be wrong, but I think it's pullet today!
Kind of sad, I need another rooster! At least they're easy to find.