Black Cat is a very simple anime. While good and entertaining and all, it just doesn't stick out that well in the sea of shonen anime. Although, average, it's done rather well.
Story: The story is pretty good. I mean, it's certainly not the best, but it's still enjoyable. That is, until you get to the last few episodes. It gets rather repulsive and disgusting, if I do say so myself. But the thing it has is consistency. No matter how good or bad the episodes get, you are always cheering for the good guys to win. You want to see the victory that these people get, and how the attain it, and how they defeat the bad guys. If you're into something like that, this anime is perfect for you.
Characters: The Heroes are great. They each have there own unique individual personalities that make them special. Train is cool, Eve is collected and awesome, and Sven is just badass! Sure Rinslet is not that great, but, the others makes up for that. I think that the flawed characters are the villains. They're just not that good. They're either assholes, obsessive, or just flat out disgusting. But, in a sense, they work. The villains are so awful, that you like the good guys even more. So, I'm not sure is that's what they were going for, but it still gets the job done.
Art: The art is rather well done. It has this sense of similarity about it, but it works. It's dark when it needs to be, and it's light when it needs to be. It's just a simple art style done right.
Sound: The OST was pretty good, but not all that great. The Opening was OK. I found myself skipping it from time to time, but it wasn't bad. If you wanna talk bad, the first ending was really bad. It doesn't fit at all, and it sounds almost as annoying as Durarara's first ending. there second ending was magnificent. It dealt with the serious side of Black Cat, and it is a smooth melody that you can easily enjoy.
Overall: It maybe only slightly different from other shonen anime, but it's worth viewing. I wouldn't pass it up, but I also wouldn't wouldn't call it a masterpiece either. 8/10