Something in the way Juliet said "I have something to tell you, and it's REALLY important" to Sawyer made me feel like she wasn't talking about the bomb. The writers have said that this season is all about the characters; well, I think "It worked" will prove to be a character-related "dying thought" and not a logistics-related one.
Remember Juliet's brief childhood flashback in "The Incident," where we saw her reaction to her parents' impending divorce? That scene was intentionally juxtaposed with one where she told Sawyer something along the lines of "Love never works out." I think those scenes will eventually get a payoff of some kind; they were included in the episode for a reason. I predict that the next time we see Juliet, it'll be a piece of emotionally rich storytelling that will bring her character full circle and explain what "It worked" meant. And I think we'll find out that she finally learned that love can work, as evidenced by her three happy years with Sawyer. And I'll bet her ability to learn that lesson will end up being somehow integral to the fate of the Island as a whole. Or, maybe it's Sawyer that needed to learn that lesson, and the critical importance of Juliet's "It worked" was that Sawyer remember that it did work, that love was/is possible.
Heck, if the writers REALLY wanted to get emotional, maybe Juliet was trying to remind Sawyer that love can "work" so that he would be open to reconnecting with his TRUE destined love, Kate. That would make Juliet both very selfless and very wise.
I'm not a shipper by any means. In fact, I'm the opposite. But the writers have said this season is all about the characters, and it would be just like them to reveal that "It worked" referred to something character-based when we all assumed it was mythology-based.