Power shuttles are great, but they still can't do all the exact same things that an HST setup can....most, but not all. Say you're building a retaining wall with railroad ties (bad idea, but just go with the concept). You pick up tie with your grapple, maneuver the tie into position, hold pressure against the wall uprights with the HST in low range, set the brake, jump down and secure it with big lag bolts. I don't see anybody doing that with a power shuttle. I also can't believe you could creep forward or backwards at 1/20th MPH or 1/50th MPH if you wanted to. My neighbor needed me to help hang the tailgate on his dump truck a while back....I hung it from my bucket teeth, raised it up, and crept forward while he stood to the side ready to slide the pins in. I was able to creep forward so slowly that getting the pins lined up was so easy it took only seconds per side. He said that normally takes him 10-15min to get everything lined up perfectly.
I don't dislike power shuttles at all, and the only tractor I own right now is a geared machine, but there are places and situations where nothing can replace an HST setup.