It's quite simply a fact that the Western media generally portrayed the Balkan wars from a one-sided perspective: Evil Serbs vs. Innocent Croats/Muslims/Albanians. This documentary demonstrates that there was a significant amount of evil on the other sides. Unfortunately, it does so while completely glossing over the crimes that Serbs DID commit. This inevitably weakens its credibility, as some will simply dismiss it as pro-Serb propaganda...which to some extent it is.
Nonetheless, there is a significant amount of testimony from journalists who covered the wars, and from US and British government/army sources, to back up the filmmakers' obvious biases. This testimony is quite compelling and I think that anyone who approaches this film with an open mind will come away realising that the issues were a lot more complicated than the media led us to believe.
My recommendation: Watch it, think about what it left out, and then read a few books on the subject.