About love being the motivation of Trip on season 4, I agree more or less. I don't think it is in any way demeaning for the character, most people are motivated by love in some periods of their lives and it can be strong enough to change a person's perception of the world.
However I believe that there are occasions that show that there is much more there. One such case is Home, where he steps back and accepts T'Pol's decision. The fangirl in me wants him to go fight Koss and do everything possible to stop the marriage, but Trip has grown and does not react impulsively any more. He is hurt, but supports T'Pol -and her mother- in what is extremely important for them, he thinks about concequences.
Then, during the Vulcan arc, he leaves T'Pol and Archer behind, in grave danger and goes out too stop a war, against orders. He becomes a true leader, a person who can think a step ahead and make hard decisions. There is much more complexity and depth in Trip than just a young man in love.
I have to agree. If Trip had broken the wedding and "rescued" T'Pol from the miarrage it would have been a bit to storybook. Instead of taking the romance novel approach where love always wins I appreciate that the writers made it more like the real world. Sometimes you have to make hard decisions. He didn't take the easy way, he did what he thought was best for her family in the long run.