It's early in the season. I compiled this chart from M-cubed of each Big Ten team's winning percentage against Big Ten Conference opponents.
Ohio State has vaulted to the top. Otherwise, it is probably about as one might expect, except I was surprised Iowa was a smidgen above Minnesota in winning percentage in that Iowa's all-time series record against Minnesota is 51-61-2. Iowa has owned Minnesota since the 1980s, but before that, Minnesota owned Iowa.
Any other surprises?