First of all, I should say how intriguing Model is, as you are first starting to read it. At a certain con (coughOHAYOCONcough) my mom bought me the first 3 volumes, just to try it out. We had to go back the next day to get the last 4 volumes, b/c I had already finished the first 3 and still wanted more.
The story in itself is very unique. I have never read such an interesting vampire story, and with such a quirky twist here and there. The ending was a bit rushed, if there isn't a better word for it, but otherwise it left you with a feeling of satisfaction.
You could say the same for the art as you did for the storyline. The mangaka surely took time and thought as they planned out each page. It wasn't the best artwork ever, but the characters were drawn well, and I especially loved the covers for the volumes!
Character personalities were fine also, and I really loved each of the characters' attitudes as they started to talk more and more about touchy subjects. I have to say, if they ever make this into an anime, I would LOVE to be the voice of Jae, the main character. She's so spunky and always knows what to say, but the down-side is that she can't seem to make up her mind when it comes to picking a lover.
Model is definitely something you don't want to miss out on, at the very least. It's sure to keep you entertained and awaiting the next volume!