Brenden,
Are you looking for a code solution, If so, accessing the underlying SPFile.CheckedOutBy property will return an SPUser that has the file in either a Short or Long term lock.
Infopath (and any other office app) would take a short term lock (I.e. for the life that the application is open) if a user opens a form for editing, but I don't think that shows up on the Checked out to column of a document library as I'm pretty certain that is long term checkouts only.
If it worth turning on the force check out for editing option of the library? This would ensure that the user name is displayed in the Checked out column?
Paul.
www.myfatblog.co.uktwitter.com/@cimaresMCTS: WSS 3.0
MCTS: MOSS 2007