I love 1st class International. I wish domestic 1st class didn't have the weight limit; it makes no sense to me that you can ship something heavier internationally but not domestically. Anyway, I have shipped to many places, Europe, Japan, South America, Australia, and have never had a missing package (fingers crossed!). It is a lot cheaper than Priority, and if you are worried, it is still way cheaper to include insurance and send 1st class.
Good luck!