Some people have seen great improvements with a new PRL, others haven't seen any change at all, still others found it only got worse. I think it depends entirely on your location. I spent a week trying out about three dozen different PRLs and found two that were marginally better than 61009, which I think is still the standard for VM.
I'm in the Eastern-most part of Los Angeles County and I ended up sticking with 60680; which I felt noticeably, though not significantly, improved my 3g speeds and consistency.