DPI deployment use case

Hello all, We have had a number of DPI boxes (SCE8080) sitting in the access network for a while now, so far they served mainly for congestion management and such, and are wondering if there are some real use case in the fine-grained service control land (as the vendors keep whispering in out ears...) Anyway, we are reviewing a couple of service manager solutions, but I would like to hear from you operators, what actual use cases have you seen in the field (if any) for DPI'ing user sessions, considering we are mostly a DSL shop. thanks in advance, cl.