I'm zig-zagging between settling on New Zealand (likely easy), Germany (likely only moderately difficult), or Japan (likely very difficult). The only countries I've previously visited in my lifetime have been Germany (three times) and Japan (once).

The answer to "why" is a couple of reasons: 1) One of my main regrets is in not taking my (briefly-attended, ultimately-failed) foreign language courses seriously when I was in highschool and in university almost a decade ago, so if I choose Germany or Japan, a few years of immersion learning -- which I understand is the best way to learn a foreign language -- will easily alleviate that regret. And it's probably a very fun way to learn one, too. The other reason being 2) Because a sudden, jarring change of pace in my life might be what I need to make my life a little more interesting, and my own personality a little less myopic and less lazy. I originally had something else here typed previously but it was long and boring: TL;DR version is that I think some sort of travel (beyond a mere two-week vacation) might benefit me both professionally, socially, and hobby-istically (yes I just invented a word on the spot), and it might be what I need to chase the boredom-gremlins away from a daily routine that currently feels like the world's least interesting movie being put on Repeat.

Expatriate living is an idea that both fascinates and terrifies me. Perhaps there's no harm in sitting it out a few more months to give it some more careful consideration (though I've been thinking about it a lot for at least three years), but time is ticking and I'm not getting any younger either...

A lot of answers in this thread have been very insightful, and will be helpful in making me arrive at a more informed decision when I finally stop pussyfooting around and make a decision as to which path I should take at this fork in the road (boring comfort vs. mysterious risk), so thank you to those who've shared your experiences so far.