I have no interest for any service or method that will falsely tweak my PR rank upwards because that would expose me to eventual counter-measures to rank me back "where I truthfully belong".
Furthermore, any web site that produces quality content will usually score a
PR=3 in a matter of weeks so it's pointless to even attempt to mess around with Google's work if that was one's "target
PR level".
If a "motivated" web publisher wants to liftoff towards the
PR=7-8-9 levels, it's a pretty risky move because the content would most likely not be "up-to-speed" for such high marks and it would look phony.
So the average web publisher looking to "accelerate his or her
PR ranking" will most probably be hunting for a
PR=5 which is mildly reassuring for the web surfers who trust this ranking to mean anything. The problem is, very few web surfers actually base their online discoveries on this ranking alone... so it's pretty much pointless to waste time trying to cheat a system that's not that important, after all.
Time, for serious web publishers, is better spent creating quality content (which gets the "real" high marks, anyway).
Although it might seem like I'm stating the obvious, I feel it's important to remind venturing web publishers that the Google PR is only one indicator among many, many others...