I installed a Pentair Intelliflo XF over the weekend. It works great and silent. I run at a low 1100 RPM / 130Watt. I do not know the flow rate yet (some 25 GPM?). It should give some ~4x electricity cost reduction compared to the old 3kw pump it replaced. That should pay for the investment in ~2 years. I'm on a TOU electricity rate plan from PG&E here in California that makes it advantageous to run the pump off-peak overnight (20c/kWh), and really expensive (56c/hWh) to run it on peak hours.
At low RPM the pump is whisper quiet. The is some minor low-frequency shaking in the plumbing, a little like a car engine idling. I cannot really find the source for that (backflow valve, air bubbles, ? ).
The only install issue is what the previous posters noted: the 2.5ID 3.0 OD connectors are a pain! What where they thinking by using this unusual diameter? Eventually I found the 3" to 2" reducers at ACE hardware, but that piece is made out of black ABS. Its visible on the picture. So I had to use a special ABStoPVC glue on both ends. That bond is likely not as strong as native PVC glue, while 3->2 reduction this is the most stressed location in the entire plumbing. But probably it is good enough. Its holding up fine until now...
One missing feature would be to be able to program the run time of the pump based on the water temperature. Currently you have to program a fixed schedule that must be changed manually (e.g. for summer/winter). The pump has a temperature sensor for its anti-freeze operation. So it should be possible to auto-adjust pump run-time based on the water temperature. That would save more energy as the pump automatically runs more in hot weather and less in mild weather.
While at it, I took the occasion to re-plumb all 2" pipes and installed a new Jandy backwash filter. I tried to avoid 90-degree turns, using multiple 45-degree corners instead. Hopefully that reduces resistance a little. I ordered the pump and the Jandy backwash valve online, at a total cost of ~$1100. It took me a full day to install, most of the time spend in round-trips to Home Depot to get the right plumbing parts.