I still have to submit the paperwork that says which country my income was earned in, which is basically the standard tax paperwork from country A plus an extra form or two. (And in years when I went to country A on business trips, it's non-trivial. Simple enough, but not as trivial as years when I was in country B the whole time). It's not extremely burdensome, but it's still one more piece of paperwork to keep track of than the tax paperwork that people who have never left country A have to deal with.