I don't know - the news station has more than a few controversies of its own.
I would take it with a pinch of salt. I sometimes watch Russia Today, and I consider that to be similar in that it's remarkably fair in British politics, giving airtime to voices slightly outside the mainstream (and to anti-EU voices in particular) but I wouldn't trust anything it said about Russia itself with a bargepole. The same is most likely true of al-Jazeera in that I wouldn't trust its Israel coverage or a lot of coverage about the Arab world. Still, it's apparently a fair few rungs higher up than Press TV, the propaganda channel of the mad maniacs running Iran, who have such sterling representatives of Britain as Lauren Booth, Yvonne Ridley and George Galloway still fronting them here - i.e. the Islamist far-left fringe (a couple of respectable UK journalists and public figures, like Andrew Gilligan, did actually appear on the station but quit when they realised the regime they were helping to defend).
Apparently, the Arabic version of the channel is a fair bit more contentious than the English-language one, but this isn't unknown in the Arab world. (See the Palestinian leadership for more examples - saying peace in one language for the Western media and war in another for their domestic audience.)