We are using Visabureau on the recommendation of friends who are now in Perth. We had a free consultation and then paid half of fee which would be refunded if they didn't think we had a realistic chance of a visa. They kept in touch by email and phone at no extra cost and advised to change our EOI at the last minute. We received our 189 invitation yesterday. They have taken away all the hassle and ,to us, were worth the cost.
Hope this helps.