The "Alt FM" format has been very popular with iHeartMedia on these translators in recent months. And they're definitely throwing it on in markets where they already have a rock station in the market... the alternative rock one has a playlist that includes stuff that doesn't quite fit in on rock stations, like Dave Matthews Band, Counting Crows, Jack Johnson, MGMT, Radiohead, Oasis, Goo Goo Dolls, The Cure, No Doubt, etc... essentially it is a lot like the Gen X format (which has failed everywhere except as a HD station in Wheat Ridge, CO that still exists on iHeartRadio) without the hip hop/R&B/dance music, and also with some newer stuff thrown in. They have launched this format on two translators in Cincinnati, where they already have a somewhat successful active rock station on the air.
Of course, even though this is the "most popular" of the current translator formats for iHeartMedia, a big difference between them and some other broadcasters (Cumulus...) is that they do put some time and effort into trying to find something that seems like it would work, and they do not necessarily insist that dozens of markets have the same five formats with the same five brands piped in from one computer in one state (at least not yet). So that leaves the door wide open... who knows? Maybe they'll throw a "90s to now country" station on there just to knock the Nash Icon station "down a few pegs." It seems that a lot of these translator stations from iHeartMedia are much commercial free, so they're obviously not selling ads, but instead have some other objectives.
As for using it to simulcast an AM station, is iHeartMedia even doing that with their translators? From what I've seen, it seems that they're taking advantage of these translators to put new content on the air, most of which are a simulcast of HD2 stations.