Lately, when sending stuff by registered mail to the US, tracking started working all the way again, after a few years of not working, so that's nice.
Once, instead of sending a registered letter (usually 10 - 20 days) I sent a postal package - for the better insurance and tracking options. Boy was that a mistake. PL to Canada...55 days. Ouch!
Of the hundreds of packages I've sent abroad by registered mail, none have ever gone lost!
Funny story; I once sent a strap to a customer in Texas. The package was returned to me two months later - addresee non existent. I emailed the girl and she told me they were deported back to Mexico

Poland is pretty good when it comes to customs not sticking their nose in and charging duties, i.e. it happens almost never. Almost.