Nevertheless I understand the notion that most of us brazilians have that tu is more formal than você, since most of us only see tu in grammar books, poems and songs. Actually even in present-day love songs - like the sertanejo musical genre - the use of teu(s)/tua(s) is very common, mainly due to this notion of tu regarded as a pronoun for poetry, and thus more refined and aesthetic.
It seems the difference is not just formality, it's also a matter of politeness. In an area where "tu" is commonly used it may be impolite to refer to someone as "tu" until you're given a signal that you can do so. At least that seems common in Portugal where you'll hear "Por favor, não me tratas por você", for example. Using "tu" with a child is not a problem, though.
I am interested in this idea that "tu" is the "proper" (formal/traditional) form when in most European languages, "Tu" is traditionally the familiar used with friends, family, and those below you in rank.
My understanding is since "tu" is used in the Portuguese translations of the bible that the Brazilians have elevated "tu" to new status.
Anyway, "Tu" is now very popular and used most often over você (easier to type as well) in Portugal and is used in the other Portuguese speaking countries so I really do think it is important to learn, especially given the popularity of Erasmus, and the Portuguese diaspora (which is more than the total current population of Portugal).
Well, to be honest "você" is not considered formal outside of Brazil. It is actually hardly used at all (except in Brazilian related ways such as, "Brazil Days"). It is actually consider the equal but unfamiliar pronoun and it is viewed as rude, crude, and uncultured/uneducated. =]
And for the record, European Portuguese is not a dialect (though it has some). :D