Did anyone get hired after using a professionally paid written cover letter and/or CV? Do you think using a resume writing company is a good idea?

This is also a business opportunity prospering ! It also has it's strengths and weaknesses.
A smart recruiter can easily make out after the interview if the cover letter and resume were bought.
Such paid up communication cannot change ones strength of communication overnight.

The resume reflects the persons capabilities, his work profile, his abilities.
If an employee uses a professional service to write his resume, it should be apt and accurate.
However, the company which reads this resume, will be going through the gradual routine of interview sessions and screenings.
Thus, the right employee will be chosen.
Thus, basically how much ever spices one person might put in his resume, will be detected at the time of the interview.
:)

I tried once this but did not find much helpful.
Such paid cover letter / resume can give you few key words, which you can include in your resume.

With CVs written by professional CV writers, the content is generally quite good but the grammar often isn't. Make sure you see samples of CVs that the company produced first - our very own bayt's online sample CV had39 (!) mistakes in it at one point (I wrote to tell them about it and hope they've replaced it since).

Preparing a resume with the help of an expert is not a bad thing. But we should understand the the specialists in this field are working on CV not from their imagination. They are collecting all relevant information from the candidate and based on these information they are preparing each CV. Their role in this task is arranging the data in an attractive way to catch the aye of recruiters. In case if you are giving wrong information and you are invited for an interview the truth will come out. Suppose you got a job by producing such a CV truth will come out sooner or later. Then your condition will be almost equal to the fox fell into mixture of fabric dye and lived in the forest in the pretext of an alien and ruled the foret. Once he owled loudly by mistake and caught red handed.

It's a good idea, since the company can correct the flaws and weaknesses on the resume.

Personally i dont agree with this and i dont believe in it. If your CV is written by a professional then you dont deserve it, while you dont have that ability.