First of all, IMHO, the only reason a manga-fan would not read this (at least once) besides personal prejudice would be the art. The art improves as the series progresses, but it is still 1996 josei art and thus crude. But I find that as you read it, the art bothers you less and less and eventually you come to appreciate the simplicity.
That said, the characters here are wonderful. Their interactions are what drives the plot, and each of them is unique in his or her way. The main character especially evolves so much... from a naive college student to a girl who is ready to grasp what she wants, all while keeping what makes her who she is inside. I have to admit, the brilliance of the entire manga is based on the subtle/unsubtle development of the main character, who is quite likeable.
NOTE: To those that say she is unrealistic in that she doesn't "fail" anything, I would have to disagree. First of all, she is talented, so she has some groundwork. But more than anything, I think what the author is saying is that if you really put your heart into something like Yuu does, nothing will feel like a failure. It just becomes a step on the staircase toward your dream. So yes, it's kind of cheesy, but not overly so, at least, for a manga of this length.
The side characters as well are well-developed. You get the sense that they each have their own dreams and goals, or if they don't, they develop them, rather than just being decorations for the plot to seem more full. Each character has their own motives and even reasons for lack of motivation, and the way the author weaves them into her plot is very slice-of-life. While the empathy will probably always lie within the main character in this one, the realism of all the characters will hold you for a long time. This manga is one of those mangas that, without the help of an episodic plot or and event-driven plot, defines itself as a character-driven slice-of-life, which is quite amazing.
The plot is just... good. There is nothing bad to say about it, nor is there any extraordinary about it. The premise of the story itself seems simple. A country girl is exposed to how life really is and struggles to find her dream. It is realistic, however, being that is driven by realistic characters.
Overall, I would probably read this manga again if I had the time. It's one of those mangas that sticks in my mind amongst the 1000+ manga I have read (yes, that includes oneshots), and every once in a while, I just have to go back and read it. It's a classic. It seems so simple, but the ideas beneath it are profound.
Read it. Preferably in one go or else you'll find yourself strangely uneasy. There are no filler chapters, you see.
It seems like it has a lot of shoujo undertones, but I don't really believe that is the case. It's more of the natural optimism that you need to face life and do the best that you can. But shoujo fans, don't be discouraged. If you're open to try new things, just try it.