My roommate and I were on a Stallone kick recently, but we never got around to watching Lock Up because we were looking for some hard (see: over-the-top) action, and this sounded more like a wistful drama. Eventually though, Lock Up came due, and I... actually kind of loved it? It's about as cheesy I had feared, but I what never occurred to me is that that cheese would totally work. I mean, it's not exactly Shawshank we're working with here, but if I were putting together a list of all the good prison movies ever made, Lock Up would be on it.
Final rating:★★★ - I liked it. Would personally recommend you give it a go.