So I'm an Obama delegate to the Johnson County Democratic Convention, which is on 3/15. I just received the rulebook, and in looking through it, I found a couple of interesting things:
1. When you show up at the convention, you go into a preference group, like at the caucuses. But you do NOT have to go into the preference group of the candidate whose supporters elected you at the caucuses.
2. There are viability rounds like at the caucuses. So if a candidate's supporters don't surpass 15% of the seated delegates at the county convention, they either have to realign or just remain nonviable and not be able to seat any delegates at the district or state conventions. This could be interesting - what will the Edwards delegates do? He got 30% of the delegates at the caucuses, after all. And I think Richardson got a few, too.
County delegates translate into a smaller number of district and state convention delegates, which in turn get translated into a smaller number of Iowa delegates to the national convention. Seems as if whatever projections are out there for Iowa delegates to both Clinton and Obama could change.
For more info, see here.