Evading a little the rhetoric that what it is really being a concerned citizen, I think it is now indispensable to have a clear and precise opinion of the political issues that occur in our nation after all not being aware of the real situation of a country to the only one that benefits is the totalitarian rulers and partisans who seek to keep their people submissive and devoted.
So yes, I think it is extremely important to be aware of the real problems a country faces in order to be a concerned citizen, after all if we are not interested in our country's political situation it is basically as if we don't care about its future.
Although my position in this case is a little pre-established by the political situation that led my country (Venezuela) to social/political/economic disaster, I consider of utmost importance not to remain ignorant of situations and problems that perhaps right now we find boring and unimportant but that if they accumulate could bring us many bad times as citizens.
In conclusion and bringing to action a great phrase of Simon Bolivar <<<An ignorant people is a blind instrument of its own destruction>>> that is to say that if we are not well informed we could soon be victims of our own disinformation.
Well I do think it's pretty much impossible to have no political opinion, since you always have some opinion. But I do think that a citizen of a democratic country should try to have an understanding of the political world, and what's happening in there. Of course you don't have to discuss the political matters, but you should have an idea what is happening, and you should be able to make your own opinion from the information you have. That's pretty important, since that citizen won't be able to properly vote for the party that really represents him when he has no clue of the political happenings in his county.
So, it's pretty important you have an opinion, but it's not important to express it ;-)