runner2: I usually only take my dog with me in the winter as she is verrrrry high energy and usually overdoes it, which means that she tends to get too overheated in the warmer months. Plus, most of our trails here are shared with mtn bikes and the dog still hasn't figured out that she needs to move out of the path of a bicycle. So I leave her home in the summer and we go for long walks at night. But she loves running with me in the winter, since she loves the snow. I second roadiegal's comment about waiting until she's older and more "fully grown". Overdoing it with young big dogs can be really, really hard on their musculoskeletal systems.

TriGirl...that's interesting that you find trail shoes more giving. But since I wore neutral road shoes, I guess that would explain why I find trail shoes to be much stiffer overall (I have tried wearing them on the treadmill and ended up with so much pain in my feet that I had to go out and buy a new pair of road shoes...and the road shoes feel so squishy to me now. I hate them!!! ).

Lauraspark, as others have said, you can run smooth and nontechnical trails in road shoes, no problem. I use trail shoes, but I run a lot of rocky and technical terrain. I have the non-Goretex ones as my feet get too hot in the Goretex ones. I run in the snow, mud, and rain and find that if I wear wool socks, my feet are fine. One tip is to see if your favorite road shoe comes in a "trail" or "all terrain" version. I know that Asics and New Balance have both used this model (I used to run in neutral NB distance shoes, and went straight to the neutral trail shoe without a problem). Ask at your local running store. But I think TriGirl's advice is right on...try it in your road shoes and if you love it, make the investment in some trail shoes.