First off, let me say that I am very light on anime, as I generally really like anime that others don't like so much (Basically, if I watched it I really liked it, with few exceptions) , so this review should be taken with a grain of salt
Characters: GJ-Bu was overall pretty good, but it had so much potential, especially the characters (Like Kasumi), which the never-progressing style of the show did nothing for (Kasumi needed more air time!).
It has a lot of good characters (Kasumi) and several of them more than deserved true development beyond forming their personalities and quirks. In short, the only
thing this show is missing is true story development (Well, and more Kasumi), which is kind of what this type of show does, so I forgive that. Even the characters you don't particularly like you can't help but not hate. They all have good qualities and give something to the show, whether it's mostly comedy, or mostly cute moments, not of them are just there as glue to keep the show together.
Sound&Art: The art and sound are nothing special in particular, but they are nice, and the style of art suits the genre of show, so there won't be any of that "This is a good show, but the art isn't quite right..." feeling you can get from some anime. (In short, Kasumi Kawaii!!!)
Setting: The show takes place almost exclusively in one room, but unlike many shows that do this, it's not EXCLUSIVELY in one room. The characters are occasionally seen in different places (For example, Kasumi is seen out on the street, and reading in her brother's room). This helps you to get the feeling of the club atmosphere because you're there so often, but not to feel like the show is trapped or that it is being "acted out" by the characters. It feels natural to be in that room because it's not constant, but you still always get carried back (I want to carry Kasumi back...).
Personal Feelings (Rant): This show was very good, but I can't help but feel like I missed out on a masterpiece. GJ-Bu had so much potential that it hurts to see it stand where it is. If there was more development in the story, and it focused more on the protagonist and his relationships with the heroines, then this show could have easily been rated a ten. In particular if the protagonist, Kyoro, and the apparent main heroine, Mao, had developed some sort of serious relationship during the show, and if Kasumi was more than a short appearance every once and a while, this show would be through the roof. Mao is where I feel really disappointed in the show because she is such a great character and had so much potential, but was seemingly given the "Never growing, never changing" curse by the writer. Mao could have easily been the best heroine of the year, but the type of show didn't allow for it. All I can hope is that some fan of the show or novels creates a doujin to give the characters the story they deserve, and that I can find it...quickly.
Thank you for reading through my rant...