My first thought when I read the description of this anime was "how the hec did they fit all that in to four 15 minute episodes!" Four episodes for four characters with seperate stories seemed a bit much. Curiosity got the better of me and I decided to watch it. I'm glad I did.
For four episodes, this anime does a lot. Each character gets their own fourteen or so minute episode (not including the ending song) and each story and character is connected loosely but clearly. Since they are short, the characters don't really develop. We simply get a glimpse of a portion of their story. It makes me want to know more which I assume is the point. My guess is this is one of those OVA's made to attract readers for the manga, but that's just a guess. Anyway, the characters feel solid. You get enough information to get a sense of who they are.
I would consider these good short stories with strong short story characters. Of course, you can't compare something like this to a full anime of 12 or more episodes and I'm not. Though, they give enough story in these four episodes to make it seem longer.
Sound and animation were good quality. I often expect OVA's like this to have poorer quality but it didn't so I'm happy about that.
Anyway...short review for a short anime. Point is, it's good and worth a watch. I definitely think I will check out the manga.
And hey, if you don't like it, it's short so it's not like you wasted a ton of time. But I would definitely watch at least the second episode. It's funny :)