I've moved my Apple account between 3 countries now - while I can't update some apps through iTunes, the updates are always available on the devices themselves, and if I try to buy an app purchased in another country, it downloads it without any hassle.
The Mac App store is a bit different - you cannot redownload apps purchased on another country (so when I reinstalled Mac OS and needed to install iPhoto, I had to revert my account to the previous country).
The Mac App store is a bit different - you cannot redownload apps purchased on another country (so when I reinstalled Mac OS and needed to install iPhoto, I had to revert my account to the previous country).