Have you regretted changing companies/jobs?

Always! For the first month.

Every. Single. Time.

Then the new paycheck comes and I'm too busy abusing it to worry about my previous company.

Yes, once. All colleagues of new company were demotivated and lame and became one of them

Once or twice
I've left about 15+ places by now and it's mostly been upgrades.
Small places, few of any significance. Wait. A good 40% were global players now that I reflect. Welp. Nike & Bruker the shed around the corner. We all play hard but at the same time and space in this universe.
Just go find something at your level

Each one has been an improvement so far, knock on wood.

Never.

I’ve only ever regretted not doing it sooner.