Nope. The projects I'm on where we use it, we're carefully migrating to the newer models. Where we can we test with evals to try and get an understanding of how the models have changed.

It's not all roses -- I've seen some regressions -- but generally the 3.x Flash models are pretty great for our use cases.

The great thing about LLMs though is it's incredibly easy to diversify and have fallbacks. But of course that means additional costs, mostly centered around engineering efforts to test and integrate them.