You may resent the Church letting those Vigil folks get a twofer
I actually resent no one getting a twofer, because I regard obligations as opportunities, not as onerous burdens to be grudgingly accepted and heaped upon the backs of others, and, if you saw my schedule for this weekend with the kids and getting everyone to Mass around practices, school dances, and basketball games, you might see that I would not mind at all if I could legally get a twofer for myself and my family. I actually had to write the Athletic Director and Msgr. of the parish where my children attend school, pointing out the conflicts between Masses and basketball games / practices / dances, of which they were not yet aware. As a direct result of my email (I suggested they cancel practices altogether tonight as a tip of the hat to the feast day), they instead added another Mass to the schedule and rearranged practices to provide more opportunity for parish school families to get to Mass for the feast day and get their kids to practices, games, and the school Christmas dance.
Regarding my opinion, it derives from Dr. Peters, and Fr. Z's disagreement but acceptance (from his blog earlier this week; I don't know if he has changed his mind since), and from what was released to us in November from our own archdiocesan office (and which all parishes in our diocese are conforming to):
Solemnity of the Immaculate Conception 2012
There have been some questions regarding Masses on the evening of December 8, whether they “count” for the Solemnity of the Immaculate Conception or the Second Sunday of Advent or might they “count for both."
The United States Bishop’s Committee on Divine Worship makes it clear that there is one obligation for the Solemnity on Friday evening or Saturday morning and a different obligation for the Second Sunday of Advent, either Saturday evening or Sunday:
The Solemnity of the Immaculate Conception of the Blessed Virgin Mary in 2012 is celebrated on Saturday, December 8. As the Patronal Feastday of the United States, this solemnity is always a holyday of obligation (except when transferred to Monday, December 9, as it will be in 2013). The obligation is fulfilled by attending a vigil Mass on Friday evening, December 7, or Mass during the day on Saturday morning.
In the Table of Liturgical Days, a solemnity of the Virgin Mary ranks lower than a Sunday of Advent; therefore, the Immaculate Conception will end on the afternoon of Saturday, December 8. On Saturday evening, Evening Prayer I of the Second Sunday of Advent is celebrated instead of Evening Prayer II of the Immaculate Conception, and Masses are that of the Second Sunday of Advent. [Newsletter, Volume XLVIII, July 2012.]
As stated above, next year, December 8 falls on a Sunday. The liturgical celebration of the Immaculate Conception will be transferred to Monday, December 9 but not the obligation.
Now that I read the above again, it seems to intertwine/confuse canon and liturgical law. But it is from my bishop. And so my family will go with the spirit of the law, which seems clear, rather than the letter of the law, which seems to have multiple interpretations, without keeping track of what anyone else does.