I have found a number of bits of information on early voting, links thereto, and a little data on 2008 comparisons. Credit goes mostly to the fine folks at USElection.org, their forum columns, but here it is in one place.
In short, Iowa voting appears well up. North Carolina voting is a small sample. In Ohio, your 'party affiliation' is the ballot you took in the most recent primary. The 2008 Ohio Republican Presidential primary and the 2012 Ohio Democratic Presidential primary were not contested, leading to some predictable but relatively meaningless movements of voters between nominal party affiliations.
The detailed information and fine links I found are below the fold: