I interpreted the watch the same way when I first saw the movie. Also that love is what made future humans bother to construct the tesseract. And that Brand got lucky guessing the correct planet and Cooper made the right decision overruling her. My interpretation was that "love" as referred to by Cooper is a force only in the sense that it propels and motivates people to thought and action they would not take otherwise, not in the sense of Brand's description as a physical, quantifiable force.
Going back and reviewing the scene, it seems more likely that the intention was the other way around. Cooper specifically states that "Love" was how he found the bedroom moment in the first place and says Brand was right and it is a quantifiable force (first 30 seconds):
Even though I think my first impression was wrong, I can still interpret the movie's love as being "a force that makes people chemically think/feel/act", as we understand it today, and not "a force that physically impacts the universe" and still fit everything pretty much into place. The tesseract is built to allow navigation via brain chemicals, those brain chemicals are quantifiable, Brand took a lucky guess. Bam! Hard sci-fi.
Even if not, the movie is just so good that I'm happy to let another force into the universe to make it work--it really just means that what present-day humans call "love" is only a surface understanding, and possibly even a misinterpretation, of this previously unknown force.
Definitely one of my favorites, and probably one of the movies I'm happiest I got to see in theaters.
It just came off as cheesy the whole "don't do the obvious logical thinking/science stuff to save the human race, LOVE will get us there". Honestly the whole Brand being in love with the other guy and his planet being the right one shouldn't have even been a need to be a thing...if Dr. Mann hadn't been a giant pussy and led them to the wrong fucking planet, they would have just been left with Brand's love's planet and gone there anyways.
This just really gets my goat when people say "UGH love" and treat it like people writing poems to each other, as if they are SO beyond "the cheese" and then don't hear any of the arguments the movie makes about it NOT being that. Well, sophisticates, don't think about rock songs and holding hands: while it's not a precise analogy, its much more like quantum entanglement where two particles even separated across vast distances are affected by state changes: Without such an intimate connection, the "aliens", who aren't able to pinpoint specific moments in space-time, need 3D humans' assistance to find such a moment to make sure that the future unfolds in a certain way. We know they get this help because linear causality gets fucked at higher dimensions because 4D time isn't linear and now my head hurts. It's really an elegant physics construct that lots of people overlook because they can't get past the word "love" and its 201X and love is for children blah blah blah.
Yes, "love" is an emotional state that has a physical effect, and yes, Cooper and Brand speculate its a connection to a higher dimension, and all kinds of things that scientists trying to make a convincing argument facing the end of humanity in a distant galaxy far from Earth might do. To sharpen the quantum entanglement analogy, love is like an entanglement with an internal shadow copy of a particle that keeps getting updated from reality, and that can get thrown off, and not get good updates, or get bad updates, or get no updates at all, and this is how relationships end or people carry torches for old flames for decades, etc.
In this movie, however, it ties Cooper to that bedroom and gives him the ability to send the message, as well as explains the "ghost" she sees in there her whole life, and really touches on the connection between a father and a daughter.
Given all the thought that went into this movie, which was started out as a script that his brother wrote, and the effort that was spent engaging Kip Thorn, etc. and all of the amazing concepts Nolan has brought to the big screen, I think that Tenet is going to be amazing.
