Differences between European and Brazilian Portuguese
Brazilian and European Portuguese are very far apart—from spelling to the use of verb tenses and terminology. In many situations, the use of European Portuguese is unacceptable to Brazilians, and vice-versa. The choice of words can be completely different and sometimes "laughable." This is specially true when it comes to technical texts, where even the choices of "imported" words are different.
A Brazilian person can read a book or hear an interview on the radio—but that is the extent of the use of European Portuguese in Brazil. In Portugal, Brazilian Portuguese would carry a lot of "mistakes" and awkward word choices and may often be considered an uncultured variation of the European form.
If we are talking about a couple of lines in a packaging (contents, or regulatory info), you could probably use one translation—but you should remember that regulations vary from country to country. If your product is targeted to a specific market niche or widespread use, you should have two translations. Another fact to consider is national pride, that is, the response of a consumer to a product that is obviously not directed to him/her.
The good news is that in most subject matters you can have a text translated for one target country and then edited (localized/adapted) for another. The bad news is that this is not a very cost efficient solution; Brazilian and Portuguese translators would rather translate "from scratch" than edit a text translated for another market, since the changes are usually very extensive, and the time required for the task might be longer than the time required to do a normal editing.
The relevance of the difference between the two forms of Portuguese doesn't apply to all situations. José Saramago, for instance, is considered a great writer in any of the Portuguese speaking countries (there are eight: Angola, Brazil, Cape Verde, Guinea-Bissau, Mozambique, Portugal, S. Tomé and Príncipe, and East Timor). The more formal the language, the easier to understand it in another Portuguese speaking country; but make no mistake, there is NO such thing as standard Portuguese.
The Orthographic Agreement
Spelling (Orthography) in Brazil and in Portugal is ruled by law, and the Brazilian and Portuguese spellings are different. Portuguese speaking countries signed an orthographic agreement that was supposed to be in place (kicks in January 1st., 2009 in Brazil). More than unifying spellings, the agreement is oriented to accept one another's spelling as correct. The agreement will not impact translations in the sense that a translation directed to Brazil will still not be recommended to be used in Portugal, and vice-versa. The agreement (in Portuguese) can be found here. Lyris' comment about it summarize very well the question.
Orthographic Agreement will kick in January 1st, 2009 in Brazil. There will be a transition period when both, the new and the old orthography will be accepted. This period begins January 1st. 2009 and ends December 31st, 2012.
This FAQ contains some articles dealing with the subject. Lyris Wiedemann wrote a very good article about this issue. The article was published in The ATA Chronicle (August, 1988) and can be found in the next question of this FAQ section.
For information about the size of the Brazilian and Portuguese economies, population, and trade with North America, please click here.