good questions.
frame material is not a deal breaker for me. I suppose I would give a slight edge to steel though.

Unfortunately i know precious little about forks. Originally I thought I wanted a rigid SS 29er but since I have a cross bike, I think I would shoot for something more different so the idea of a 26" hardtail came about. I don't plan on doing big jumps so 160mm sounds like more travel than I would need. I guess I would shoot for a fork travel that is well established so there are lots of good forks at various pricepoints available, but I don't know what that travel range is (I would guess 80-100mm).

I mentioned the Surly mostly because I'm familiar with their road/cross bikes so I know they build really solid stuff for reasonable prices. I think keeping the option of going rigid is nice but I'd want a suspension fork to start with.