I can tell you that I would have bought many, many albums if things like bittorrent didn't exist. Since I can just get mp3's from bittorrent or my friends, unscrupulous people like me can basically get unlimited free music, although I do often buy music on iTunes to get a high bitrate non-defective copy of an album I especially like (Tea for the Tillerman, Neon Bible, Trial of Van Occupanther). I hate going to concerts, so I only do it when people convince me to go along, and certainly no more than I would if music wasn't free. The bands I like are probably about the same as the ones I liked pre-filesharing, minus ones I've grown out of (Tool, Radiohead, Weezer -- I've bought albums from all these bands pre-filesharing days) plus ones I randomly found on iTunes, plus ones I heard my wife listening to or on Last.FM. I haven't found any new music via filesharing really.
The argument about filesharing is that it is impossible to stop, so attempting to do so is pointless. The amount of government intervention necessary to effectively end sharing of music (and thus violating copyright law) is so draconian that given the balance of (good done by enforcing law) - (harm done by enforcing law) is extremely in the negative.
When the government tries to enforce laws that people will not follow, it does great harm to people's respect for the Law. Marijuana laws, too-low speed limits and other laws that are ignored put people in the habit of ignoring the law if they can get away with it. While Jeffersonians like me generally see this as a healthy attitude (as no one gets hurt), it should still be our goal to establish laws that aren't bullshit, if only for practical reasons (like using the police to work on crime that we actually care about instead of people going 65 instead of 55 on a flat, straight highway).
Since there is no way to stop filesharing, and reducing it at all will involve huge monitoring of the internet, fuck it, change copyright law to reflect reality, and let big music publishers join horse-shoe makers and coal delivery men in the history books.