It has made some difference on my unit, with conversations all the sudden going ultra quiet. but it will not increase the loudness overall. If your on sprint you will need your MSL (vzw leaves theirs blank, a la 000000) you can call for it, but you will have a hell of a time or you can try bitpim see
this thread
oh, and this isn't exatly a reg hack either, you are actually chaning the settings of the phone chip