I agree with Randy. There is no need to go to an immigration lawyer, unless there has been some problem. For the vast majority of cases, you fill in the forms, and join the process like everyone else. A lawyer will do exactly the same - they fill in the forms for you, and send them in. Save your money!
I can't tell you whether you should use a lawyer to help you with your application because that depends on you. It's like asking "should I hire a painter or do it myself" or "should I hire a landscaper or do it myself"?
Many people seem to say "are you kidding, painting or cutting your grass is very easy, why would you want to waste your money on someone else helping you with that". What they don't seem to understand is that what's easy for one person may not be easy for another. It's also not always about if it's easy but about time, effort, & efficiency. A helping hand and guidance can go a long way for someone who is busy or uncertain about the process and doesn't feel like reading up on paintbrushes or what seeds to use.
For something like painting or landscaping, it's not a big deal if your ceiling cuts are a little crooked or your hedges are at a slant. But for something like immigration, a good and complete application can make a huge difference in your future.
The point to all of this is when someone says "why would you waste your money, just do it yourself, it's easy" bothers me because it's very inconsiderate advice since some people could really use the help with something as important as this. But for some, it could be great advice if they are comfortable with research and following the guides, easily accessible from CIC.
So that's why I say it depends. Are you comfortable with forms and instructions? Are you willing to apply focus and effort to follow through with your application? Etc...
Whatever route you take is fine but it's your choice and not for others to decide for you. If you choose to use the services of a lawyer, just make sure that they are a member in good standing with the Canadian Bar Association which can easily be looked up online. The Campbell Cohen law firm you mention is run by David Cohen and he is. As for Gomberg, I don't know.