I have the Nikkor PC-E 45mm and 85mm and love them. But it seems like the Canon 24 is a little better for me than the Nikkor 24, mainly because the Canon has virtually zero distortion.

I think the latest Canon 24mm and 17mm are both supposed to be awesome, so I'm not surprised to hear you're loving the 17mm. I've never personally had much use for something quite that wide, but 24mm is one of my favourite focal lengths so I'm about 99% decided on the Canon 24mm.