@ otise
I guess like it has been said over and over; when it comes to agents; it just depends on which one you have used or which side of the river you want to be for you to be considered as been on the other side of the river.
They neither speed up nor help you in any way, shape, form or manner. If your case is straight forward, I say go ahead and try on your own. Read up on the CIC guideline for the particular stream you are interested in. The document checklist that you have to include in your application is a great tool as it ensures you have not missed a thing, plus you can always come back to the forum for any clarification. Like it has often been said, the most stupid question is the one you failed to ask.
If you are still curious to see the process / rules for assessing your applications or for further enlightenment, see below links. Between these two documents lie all the answers to the various head "scratchers" you may have wondering what and why are the VOs doing what they do.
1. Operational guide for MI 8
http://www.cic.gc.ca/english/resources/manuals/op/op06c-eng.pdf
2. The Immigration and refugee protection regulations from which the various regulations cited by visa officers in all letters are drawn
http://laws-lois.justice.gc.ca/eng/regulations/SOR-2002-227/index.html
After all said and done, if you need to use an agent, I guess the owner of this website
(David Cohen) will be one to consider. Think about it, he is comfortable in the knowledge of what he knows he can bring to your case
IF you decide to use him that he provided you a platform
IF you decide to do it yourself.
I have not used or dealt with him, but if I need one, I guess it will be my logical thought. I will rather err in that thought process than land in the hands of some "cheap quack" that probably just has a website hosted and works out of his living room. Come to think of it, we only talk to them on the phone or did anyone visit these agents in their office before you hire them?