Well, since nobody got back to me I figured I'd update anyone interested in going to Milwaukee.

Exec aisle had Impalas, a Forester, and a Regal with about 5k on the ODO which I took.

Regular aisle was Impala/Malibu everywhere.

Funny thing is when I rang them up after I rented to change my booking to a one-way to O'Hare, they suddenly told me that they had cars which needed to go back to O'Hare, which included a 300, an Explorer, and various other solid Exec Aisle rentals.