My question, to anyone who has knowledge of getting paid directly in BTC - do you negotiate your salary directly in BTC/year, or in some USD of BTC per year?

For the former, let's say you negotiate a salary of 100 BTC/year. If you negotiated this in January 2016 it would have been close to $100,000 per year. But now you'd be making over $400,000 per year. The upside would be tremendous. But obviously the downside would be huge, large enough that if Bitcoin crashed you might just quit your job.

On the other hand, if you said pay me $100,000 worth of BTC per year, it's not clear what the upside of that would be. It'd be safer, but it wouldn't be fundamentally different from just getting paid USD directly.