Personally I think it's hard to really not like Vincent. I felt like everything in the game was written solid and acted out solid, with some nice metaphors for relationship drama. It's worth a play through for the experience alone, and it's one of the best handled localizations I've seen in a long time.
It's hard not to relate to some of the thoughts that goes through Vincent's mind based on the choices you've been picking. I found the experience just incredibly engrossing, and the ending I got the first time, while bad, felt like it was something I honestly deserved. Yahtzee was also spot on in terms of the game play, it's frustrating in the sense that you want to keep playing and overcome it. Without spoiling anything, the fact that Vincent's two love interests are both named Catherine, makes for an interesting final act.
That aside, much like the Persona games, the socializing aspect really feels just like an opportunity to learn more about the characters, which is probably what I wanted to play the game for the most due to how much I enjoyed the writing, and at least unlike Persona you're not compelled to actually go on with the side stuff since you don't miss out on anything different in the game play.
With all that said, it was an entertaining review. I didn't expect you to review it though since it hasn't gotten a PAL release yet.
EDIT: One thing I will say about your review that I didn't get personally was that Vincent not telling Catherine that he's in a relationship already is purely down to it being an anime inspired thing. It's clearly established in the game prior to him meeting Catherine that he really has no intention of jumping into a marriage what with him being comfortable where he is, and that Catherine symbolizes the thrills and freedom that Vincent is longing for, since he feels that he's not sure he can conform to this new, demanding and imposing side Katherine is showing off. The reason he's a tool is because of his indecision over finally taking responsibility with his current love, or continue living life through his own will and accord.