I dont have any way to say thats not right, but for me the 70 update has improved my 3G speeds.
I think the 60669 PRL - PRI has problems. I have also seen a few other threads where people have been having problems with poor 3G performance. Since the upgrade to 60670 I have not had the problems.
So for now based on what i am seeing with my data speeds back to normal, and several other people saying the same thing, its a good possibility that updatin go the new PRL will help.