HPR is interesting stuff. As some have noted here, you do lose a little low end torque and efficiency. But thanks to the high cetane, cars to start easier, idle smoother and might have a little better top end power.
The downsides are that on old VE pumps with already very old, marginal seals, the complete lack of aromatics make old seals shrink and harden worse than the switch to ULSD. That having been said, if you have relatively new seals in the pump, no need to worry. A leaking pump is not a "failed" pump.
Conventional biodiesel is disappearing, at least in 100% concentrations, because CARB has found it to produce more NOx than regular diesel. While it may be cleaner in other aspects, as we all know, CARB has it out for NOx pollution. CARB is the reason retail stations are not allowed to sell 100% concentrations of conventional transesterified biodiesel. Not to mention, it has its own negative side effects. I know of one well known biofuel station in the Bay Area, in order to keep their retail product 100% renewable, they've effectively been blending biodiesel with HPR. Retail stations are allowed to blend upto B20 still, I believe. It's just the B100 that's difficult to come by.
HPR does reduce every single regulated emissions from the testing I've seen, including NOx. And most noticeably to those running modified or otherwise somewhat smoky old diesels, the soot production is far less as well and the difference is easily visible with the naked eye. For those with DPF equipped vehicles, this means more time between regen cycles because it will take more time for the filter to get to the threshhold where a regen is started, and thus you will ultimately have fewer regen cycles through the life of the vehicle. This is not a bad thing.
For those with LNT-equipped gen 1 commonrail TDIs, this means it may go a little longer between the micro-regens required for the LNT to work effectively due to lower NOx emissions. For SCR with diesel exhaust fluid equipped cars, this might mean a slightly lower dosing rate of DEF.
There are trade offs. It's not a perfect solution. And since my corner of the bay doesn't have an HPR station, I more often just opt for D2 anyway, plus, I get better low end torque and fuel efficiency, so there's that... If there was one closer, I'd likely alternate between the two pretty frequently.