From the beginning, Sophie was quite the puller when we walked her on a leash.  We've had her for two months now and we've been working with her regularly and have come a long way. We walk her with a halter that attaches at her chest and she's way better than when her regular collar is on.  We've made great progress and while she still likes to keep some tension on the leash, she isn't really pulling anymore (unless she sees another dog, people, a stroller, a squirrel...   Without distraction though, she's now walking well on the leash.

I know Sophie is still too young and I think I'll have to wait until winter 2012-2013 to try skijoring. But my question is this:... will all this work to have her walk nicely on a leash affect her willingness to pull when we finally get to try skijoring?

I don't believe one has anything to do with the other.  I believe you could train your dog to "Heel" - walk along beside you - and not pull with an appropriate command, and then allow it to pull, as in skijoring.  I train my dog to "Heel", and then "Hunt" (for example).  Heel is walking within 4 feet of me (within leash range), and "Hunt" is to range out.  For obedience, I keep her at heel, then tell her ot "Hunt" (she jumps out and ranges/runs/quarters) and then tell her to "Heel" again (and she returns to leash range).

Different collars/harnesses help as well.  For some nice, affordable harnesses, check out www.alpineoutfitters.net.  No, I do not work for them...