I am in a dmp right now. Ive been in it since 2/08. My average interest rate on the cards is probably between 10-11% and my monthly payment is $1261 on $54k of original debt. Its now down to about $40k. It was good for me because before I did this, I was churning, just paying the high interest rates, but not bringing the principal balance down. I think there monthly charge is about $25 but the rates they got for me make it worthwhile because I will soon be out of debt completely and have my credit still intact.
I finished my DMP in Dec 07. I had about 70k of CC debt and my payments were around 1400 a month. If you can afford the payments, DMP is a good option. it forced me to live on a budget which I still do today. In terms of affect on credit, since DMP I got a prime Visa card, auto loan at the best rates my CU offered and a mortgage refi at 4.0%.
I sent you a PM of the DMP compnay I used since we cant posts links to them here.
Do not use the services of a Debt Settlement company since that will ruin your credit and probably rip you off. IMHO better to fill BK the go that route.