I wouldn't go so far as to say cult since it can be quite a relative term.... I typically consider any theology that strays from the core christian teachings (Christ the Son, the Holy Trinity, etc) as cults, so my idea of a cult would be like JW or Mormons, Unitarians, etc.
My issue with Hillsong is the fact that Brian Houston was found by the Royal Commission to have acted wrongly in regards to his fathers child sex abuse allegations (which his father actually confirmed). Brian as president of the then Assemblies of God did not report these things to the police as he was obliged to do, and did not step down at the national board meeting about his father, he was chair man of that board and the RC found that he acted in contravention of the AoG policy on pedophilia... Essentially he gave his father a retirement package and supported him with ministry money for the rest of his life and did not refer the matter to police. The victims did not get an apology or anything from the board.
I really suggest people go and read the RC submissions, specifically no 18 and another about Hillsong (can't remember the submission number). Before they go on the defensive to me and try to dismiss the situation, I actually did take the time to read the report in full and it really disturbed me, there are many other questionable things in the report about Brian's involvement that I haven't even mentioned, like the victims interaction with Brian which he allegedly said "it's your fault, you tempted my father", that he refused to help his NZ colleagues with the abuse cases relating to his dad that arose there, that his father was not infact "excommunicated from the church" as I heard his proponents say but that his fathers credentials were strip for 2 years pending determination by the church which he was then allowed to make an application for their reinstatement at the national board meeting, the fact that they offered his father counselling and a 'restoration program' contrary to their policy on pedophilia and did not offer the victim anything of the sort, etc. My point is that all these issues related to the current head pastor, Brian Houston's role in his fathers defense, Brian was president of the AoG, and acted completely inappropriately and with a conflict of interests regarding his fathers discipline which he oversaw.
This was in fact one reason (along with many others, mainly to do with theology) that I left my old church because they use Hillsong music and actively support their conferences. To me, the lack of sensitivity to the victims and accountability of Brian Houston's role disturbs me enough to steer clear.