FS is just another example of a different way of DJing tunes.
Some people moan about CDJ's, on the grounds that "it's not proper DJing" if you're using CD's. Yet most clubs I walk into these days seem to be decked out with them and I've seen loads of big name DJ's using the all the time - and it's definitely a great way to be able to play your own tunes out straight away.
Some people moan about using Traktor on a laptop to DJ, on the grounds that "it's not proper DJing". However, I've seen a lot of people - particularly in the breakbeat scene - use it to devastating effect. Making their own edits of tracks, mashing in acapellas, jumbling up loads of elements on the fly to create something a bit different.
I've even sat and listened to some people moaning about using Ableton Live, because it's not as visually stimulating as watching someone tweaking knobs... or something (mmm, yes, we all go to watch really, don't we)... Yet, in my opinion Ableton Live is one of the most creatively refreshing bits of software to come out in years.
And so, on to Final Scratch.
People moan about it because of the sound quality, because people are stealing the music, and because it may or may not be cheating. The fact is that all of these things are true to some extent, but it also offers up a lot of other possibilities to the DJ that are not available with traditional vinyl alone. (On a side note, it is quite fun to use).
To sum up... I quite like all this new stuff - it keeps life interesting. Everyone (hopefully) can do something a little bit different to everybody else, and music as a whole becomes a bit more varied. Technology bounces forward at a hell of a pace, and I find iit quite interesting and exciting personally.
However, each different person is going to have their own "tolerance level" with reference to how much technology they're prepared to embrace - and I suppose you have to respect that.