Here's the deal: Of course your credit is going to be affected because most of your creditors will close your accounts bringing your available credit to zero. As you pay, your balance goes down and your scores will gradually go up. It is a process.
There is a notation that some of the creditors put on the credit reports saying you are in a dmp or something similar. Some creditors do not put the notation. However, the notation is removed once you have completed the program or terminate the program.
You pay back 100% of the balance with less interest with a debt managment program. That is better than bankruptcy or debt settlement. Debt settlement is not a road I would choose. What people don't understand is that even when you settle with a creditor or collection agency for less than full amount, sometime you will still be harassed for the amount you did not pay or worse yet, get sent a 1099C from the agency saying you owe money on the amount you did not pay and this is reported to the IRS. Also, you will have a notation of "settled for less than full amount" attached to that tradeline on your credit report which is extremely difficult to get removed.
The bottom line is: You got yourself into debt...you need to man up and get yourself out. Personally, I am one that believes you should pay back every dime you owe and prefer the debt management programs. Every one is different and every financial situation is different. You need to research programs that are out there and ask questions. I did this and decided to go with Incharge. They have been very honest and helpful. I would highly recommend them.