I have and can validate its fairly accurate numbers for FAANG / SV salaries but not so much European ones.

It also gets hairy once you compare pre-tax (US Salaries) with post-tax (EU salaries) and different costs of living.

I use a combination of levels.fyi, Payscale/Glassdoor plus Numbeo / Nomadlist to keep running the numbers around how much I could save by moving elsewhere.