If Zechariah deserves any sort of contempt regarding his failure to accept the word from heaven as a wise and learned priest within Israel's tradition, then Simeon deserves a great deal of praise for his moment of understanding when faced, not with an angel speaking words of victory, but with a helpless child in the Temple. Whereas Zechariah balked in the face of God's promise, Simeon receives God's activity. That which we can see in this old man's final moment of waiting is the convergence of God's covenant and Spirit.
When the infant Jesus is born, he is to be presented at the Temple. This is to fulfill the covenantal law for the people Israel, both for consecrating the child and for purifying the mother.
It is debated whether or not Simeon is a priest in the Temple, and since Luke does not mention this specifically it is most likely that this is a fervent watchman and not part of the formalized levitical order. (He is described in every way that one would expect for a priest, but is not specifically mentioned as such, which would be rather odd if he were.) Further, this is not the scene of circumcision as is sometimes assumed, for Mary is still present which indicates the context of this moment is found in the outer courts of the Temple where women would be admitted.
We are told that he comes to this place in the Temple at this particular moment because he was 'moved by the Spirit' to do so. So, quite literally, this is the moment at which Law and Spirit come together around Jesus - it is summarized in Luke 2:27. But this is more than a physical or geographic description, it is a theological assertion that this child represents the coming together of covenant and Spirit - the latter giving fulfillment to the former. As such, it is why Simeon's waiting is completed and his dismissal now appropriate.
His eyes have seen God's salvation, which is happening in the site of all nations. This promise is being fulfilled in the face of tyrannical rule and foreign occupation of their holy nation. It is taking down the oppressors and bringing in the outsiders as God's glory comes through his chosen nation. It will not be without pain and sacrifice, and it will reveal the hearts and motives of many.
From this moment through two millennia this rings true. For, in our world we can still welcome the still, small voice of God in the midst of the earthquakes, winds and destruction of the evil which storms around us.