First of all, don't be dissapointed. This series contains cat girls as well! :)
There wasn't really much of a story to dog days. Some random guy got ported into a world full of dogs and cats, where they have friendly or not so friendly battles with eachother just for the sake of having battle(and money)(while typing that, a strange image of america came up with me, I don't know why). This kind of story has been done before, and it just had nothing new in itself(except for the cat and dog girls. Oh, there were guys as well, sometimes, in the background). So no a high score on the story part.
Dog days was very colorful, which I liked a lot. Because dog days is all about happy battles that sort of style suited it perfectly. I also liked it that the main characters were 10 times more detailed unimportant random battle dudes, who all had the same face.
Barely passed the grade on this part, the characters all sounded way too squeaky. The opening song was very forgetable as well. As was the ending song. I guess I must´ve liked the ambiance to still give it a passing grade on the sound.
First of all: There were just too many. The serie had like 3 main characters and 50 billion side characters. I had the feeling that the characters which actually had an expression on their face should've played some part in the plot, but just didn't. They did get some lines of text, just enough to make me interested, but not enough to satisfy me. And the main characters story sucked big time.
Dog days was a very lighthearted series, which I liked at the time of watching. After looking back though, I noticed that there wasn't all that much going on, and that it completely lacked any sort of progress in the story(other than some characters liking each other more and more. Yea, what else is new?). So if you want to have some eye candy in the form of cat girls which doesn't require your brain to digest: Go for it. Just don't look back on it later.