[1] Google data centers can achieve a PUE (Power Usage Effectiveness) of less than 1.06 [2], so I don't think a PUE of of less than 1.02 [3] achieved with immersion cooling is spectacularly impressive.
[2] https://www.google.com/about/datacenters/efficiency/internal/
[3] http://www.allied-control.com/publications/Full_Version_Bitcoin_2-Phase_Immersion_Cooling_and_the_Implications_for_HPC.pdf
Saving 5% on electricity is definitely important for any large datacenter and the methods google uses to cool are very extreme and expensive.
The average datacenter would save something like 20% on electricity costs in addition to the high density as you mentioned.