i actually found that sharing my mixsets and my own early tracks on slsk got me a HELL of a lot of publicity that i probably never would have gotten.
one of my earliest tracks, which sounded like crap but was a reasonably good tune, i gave to a couple of friends and within a week i was getting PMs from ALL OVER asking if that was my track. i have no doubt that led to more people picking up my records when they did come out. i have seen some of my released tunes on slsk, and while i want people to support the labels and buy the vinyls, i know that my stuff is getting out there.
there have been many attempts to squash filesharing and none of them have really worked. i, like one of the posters above, know that it's here to stay. so i figure i'll make the best of it and use it for what it's worth.
i have bought many of the records that i have downloaded on mp3 and conversely, i have downloaded a lot of the records that i already own in order to avoid having to encode them when i (hopefully) get serato scratch. since i don't have it yet, sometimes it's nice to burn off a few cds of stuff i have on vinyl for gigs, since i don't generally like bringing more than one record bag.
there is always going to be a downside to filesharing, but i gotta say that for me, it has been a great publicity tool, and i will keep using it in that manner. not to mention i have met tons of techno heads from all over the world and had some great conversations. :)