I personally use the PS lub additive,and equate it to the Deer whistles we used to put on our front bumpers in NE to prevent deer hits. I can tell you they work because I've never hit a deer. When I do hit one I'll change my mind. Same with Lub Additives. My 2009 TDI is running fine thank you and I've not hit a deer yet.
Aww crap. Now I need a deer whistle.
Whole issue seems pretty simple to me. Assuming additives do no harm (interesting point of discussion), the cost benefit tradeoff is the cost of the additive measured against the risk of failure and whether adding the additive decreases the likelihood of failure (another main point of contention).
Since the cost of an HPFP repair is high and the cost of the additive is relatively low, even a modest reduction in likelihood of failure has some value to me.
If there was a fuel pump that you KNEW without a doubt contained diesel with an HFRR under 300, how much extra per gallon would you pay to pump that fuel as opposed to unknown fuel? My answer is about 10-15 cents.
Optilube costs 7 to 15 cents per gallon of diesel (according to their website).
Now if you buy into the idea that the additive will pay for itself in increased fuel economy (I'm not at all convinced), it really becomes a no brainer.
That logic holds pretty tight unless you think the additive might damage your vehicle (decreased DPF life?), that using an additive doesn't increase lubricity, or that increased lubricity doesn't extend the life of your HPFP and decrease it's likelihood of failure (which is pretty well proven in my opinion based on the presentations from Bosch showing the relationship between wear and HFRR).