I always train with an I-pod, and brought it for the Disney half, but didn't take it out of my fanny pack at all. There was so much to see, and so many people to talk to that I didn't use it, and didn't miss it.
On the other hand, I did use it during the Philadelphia Distance Run last September. That was my first half, and there is a pretty long stretch with no crowd support, and the music really got me through it.
Hmmm . . . maybe this wasn't very helpful! I guess what I would say is that I have no plans to stop using my i-pod during training runs. In fact, it makes a huge difference to me to have music for those long runs! But race day is really different than a training run. I think I will continue to bring my i-pod with me to any race 10K or longer, and will use it only if I really need it to get me through. I have learned to just put in one earpiece so that I can still hear what is going on around me.