Hi there
My best friend used an immigration laywer and said she was really pleased to have done that as everything was always in order at the correct time, however we decided not to as i thought the procedure was quite straightforward and rather than pay someone else I would do it myself, all of the information you need to complete the application and gather your documents is on the CIC website there is a world of information there and on this forum to guide you through it.
But should you need any help with anything then the members of this forum are always ready to lend a hand, and give really good advice.
I would say that unless you feel you have a problem that needs expert advice ie a criminal background then as long as you follow the instrutions and gather everything you need it is easy to do yourself.
Hope that helps
Libby Lubby x