Yeah there's never any guarantee, but a good packer can make all the difference.  The guy i've been using in Japan double boxes everything and even when I get a package that is nice and rounded from excessive handling, the items inside are always just fine.  Usually I'm shipping larger/heavier items.  My typical slowboat package consists of a pair of X68000s and some random stuff usually weighing in at around 40lbs.  Cost to ship is usually around 10000 yen or about $131.
If you can wait, surface mail is great and cheap.  Another option for lighter items is SAL shipping which is kind of halfway in between EMS and surface hehe.