I'm just going to say it up front - I really hated the artwork in this one. I don't know if it's the author's particular style, or if they chose to do it this way on purpose, but in either case it's really not very good. In fact, when I first started reading this I questioned whether I would be able to get through it simply because of my distaste of the artwork. And, unlike other art styles that start off terrible, but improve as the manga goes on (think of the the difference between the first chapters of Ah! My Goddess as compared to the more recent ones, for example), this one stays consistently bad throughout the course of the story.
But you know, with all that said, by the time I was halfway through the first volume I really didn't even notice anymore. It's just a great, great story with interesting characters and a fantastic "hook" that sets it apart from the majority of other romantic comedies I've read. True, there are other stories where the main character is honest to a fault, gullible, etc., but they're usually done in a "fish out of water" type scenario, where the person has been living outside of normal society for whatever reason. This is the first manga I've read that doesn't use that approach, and it works remarkably well.
So, an interesting story, great humor, lovable characters, and a genuinely touching romance override whatever faults there may be with the artwork. If you're a fan of the genre, give it a shot - I don't think you'll be disappointed.