@MrMoody, Nony: I can confirm that proving rings are still used in laboratory apparatus, although electronic force measurement instruments are used more often these days. The drawbacks of proving rings are as follows: Proving rings exhibit a reasonable amount of measurement hysterisis.
Proving rings can store a lot of potential energy, which means that they can fly off if something goes wrong. It also means that your system may be hard to control displacement with.
Finally, mechanical dial gauge based proving rings cannot record results automatically, which often means lots of time writing values down.