I beg to disagree. Some consultants are excellent, however I would advise, in case OP needs one, to carefully chose his/her consultant.
My case was not straightforward and I contacted a few consultants for advice. Two of them gave me different replies to some of my initial questions, notably about common-law partnership. I did some research myself and hired the consultant that was right and has a long similar experience. A lot of consultants out there don't necessarily have a long immigration experience but yet sell their services (not illegal at all). It is good to check the LinkedIn profile of the consultant to understand his/her background.
No doubt OP can get a lot of information from the forum, which for a lot of people suffice. It really depends on how much time OP can devote to this application and how complicated his/her case is.
For my part, I decided to hire a consultant. It was expensive, but I don't regret it at all.