I've read this manga about 3 times now, and it's a pretty odd one. As a whole I like it a lot, but it really drags here and there. The main character is infuriating, yet there is some satisfaction in how he grows, though I can't really say if it was worth suffering 140 chapters of it. The main heroine, on my first reading I thought she was pretty shallow, but she does have some depth and I think Masakazu did a great job showing her character subtly through her facial expressions.
With that said, the first few arcs are really hard to read. The first arc has a classic feel, but it's also the protagonist at his most infuriating point. It gets better, but there are times when it gets worse.
The entire ending does make it feel worth it, though. The entire final arc is better than the rest of the manga by a mile.