Basically, they dispute your negative marks with the creditors, credit bureaus, and collection agencies.
i had about three years of being very very irresponsible with money (ages 18-21) and although i'm good now, my poor credit score is still following me around.
have you guys used any of them, or know anyone who has?
Sounds pretty expensive to me. you can attempt to do everything that they can do for free. all you have to do is dipute the items with each company, they have so many days to respond and if they don't respond...then the item is changed or removed.
The deal is that these companies are busy and often don't bother to respond to something that is a few years old or they just to get to it in time and then you win...but if they do respond then the investigation will show whether the info was correct and it will stay put.
honestly, they won't do anything that you can't do yourself for free. check out creditboards.com for advice. I cleaned up a lot of things on my report myself...it takes a little while but it was worth it to me not to have to pay!