We didn't use an immigration advisor for our (admittedly straightforward) visa application under the Skilled Migrant Category. For us they would have been an expensive way of adding an extra step in the flow of information between ourselves and INZ. I found the information on the INZ website (and indeed this forum) to be helpful and up-to-date. I spoke to INZ on the phone several times for clarification and they were very helpful. I found that being organised with your evidence, being honest and open at every stage made a big difference. For me it WAS a form filling exercise but I can see how for others it may not be. I can see how an advisor would be invaluable if your application is not straightforward or you need that extra help.