I've had some luck recently with GW letters. I sent out 5. Still waiting on 2 replies. I got 2 that agreed to delete and one that didn't. One that I'm waiting to hear back from has also disappeared from my most recent Experian, so I kind of expect to get a "yes" letter soon.
I say go for it. It's only a few stamps and a couple minutes of your time and it could get you some points in your score.
- Catz
12/01/09 TU 759 EQ 756
10/01/08 TU 697 EQ 659
07/05/08 TU 693 EQ 663 EX 711
06/01/08 TU 657 EQ 610 EX 670