I did my PR through David Cohen's law firm (owner of Canadavisa.com). Had pretty good experience. Although I had to fill out all the forms myself but the law firm verifying everything for me and asking for more documents to solidify my case was a great help. I would have never provided all those documents that they had asked me to submit if I'd handled my case on my own. I always thought that all those additional documents were unnecessary but turned out every single doc I submitted helped my cause.
People you deal at Cohen's law firm are very professional. They assign different case manager at different application stage. Although, they have very strict code of ethics but I found one thing very annoying that they charged me for all FedEx mails that they sent to CIC. FedEx cost was no where mentioned in the contract I had signed with them but it was really a small thing. Bottom line is that I am a very satisfied customer, currently sitting in Canada. I would highly recommend them to anyone.
The best thing about them is that they will neither encourage you nor submit any false information or fake documents to make your case strong. If there is something which is absolutely required and you can't provide it, they'll clearly tell you that CIC may not like it and may reject your case. No false guarantees which really gives you piece of mind and assurance that whatever they are doing is in your best interest.
When I signed up with them I was told that I'll get my PR processed in one year but it literally took 3 years but again its not their fault. CIC was very slow in responding. Another thing I liked about them was that as soon as their communications department received any email notification from CIC regarding my case, they always forwarded it in few minutes. I had never had to ask for an update.
All in all, very good experience.
Disclaimer: I have no association with David Cohen's law firm. Whatever information I provided above was my personal experience while working on my case with them.
