Run The Floor recently broke down Oakland University, basketball-wise, as it relates to the Horizon League. Here are some highlights:
"11 - The Golden Grizzlies are 7-4 against Horizon League teams (counting only Valpo games from 2007 onwards) since 2003, in 11 meetings."
"151 - Oakland's Pomeroy ranking at the end of the 2011-2012 season. Cleveland State (83), Butler (110), Detroit (120), Valparaiso (147) and Milwaukee (150) were higher, but not by much."
"$1,555,472 - Oakland spent that much on their basketball program in 2010, according to the most recent numbers available over at BBState, which marks them as solidly mid-major. That number would rank them eighth in the Horizon League, ahead of Green Bay ($1,409,931) and Youngstown State ($1,022,407)."
The story also mentions the Golden Grizzlies would make sense for the Horizon League from a scheduling aspect, pairing them with Detroit as a travel partner.
"Also, since the league depends on "swings" in its scheduling where teams travel in pairs, Oakland and Detroit would make perfect travel partners a la UIC and Loyola in Chicago. Under such a plan Valparaiso and Wright State would also become travel partners with Butler gone."
The story calls Oakland the Division I front-runner for the vacancy, but mentions the conference could go with a Division II choice as well. 
Oakland coach Greg Kampe talked at length about a potential move to the Horizon League on Tuesday's season-ending edition of "The Greg Kampe Show" on WXOU, examining these factors and then some.