Has anyone had bad experiences with these companies?

Yes.  Mostly because my exhusband was court ordered to pay certain bills.  I called the companies and let them know, I made sure they had my name and address at all times.  he defaulted on a bill and didn't pay it and then they sent collections.  I explained to the company about the court order and we went to mediation.  My exhusband set up a payment plan with them but they still left the black mark on my credit even though I had court papers that said he had taken out that loan without my permission. 
Forget trying to get it back off the most they do is let you put a note on it.  Bah.

Was the collection paid? Was it a charge off? If not consider a pay for delete.  Or Dispute it as not mine. It may take a few cracks but it should come off, all three credit bureaus.

That does suck.  It will completely fall off your credit report in seven years.   Wouldn't a default be similar to a late payment, because I know one or so late payments do not effect your credit by much.

I have dealt with these people. They are rude and try to intimidate you. There is no way to even talk to the people who call. The people who do the calling are just average people who don't care about you or your problems and refuse to listen to you. It's hard to even get them to put a supervisor on the phone.

Part of the problem with having to deal with credit card debt is having to listen to creditors calling all the time

Luckily I haven't had to deal with them in years. I'm managing to stay out of that trouble and am paying my bills on time. But many years ago I use to totally dread answering the phone. They're rude and insensitive. I'm just glad I am out of that situation. I'm really trying to not let it happen again.