Kujibiki Unbalance, as I understand it, was originally just a "show-within-a-show" on Genshiken, a fictional creation that the characters of Genshiken would talk about and debate, and we would be entertained with alleged clips of Kujibiki Unbalance during Genshiken. Although inspired by this source, this telling of Kujibiki Unbalance is its own story, quite capable of standing alone on its own. It differs slightly from the KU as seen in Genshiken, and some fans do no like this fact, but I personally did not mind. It is a solid, fun story; the characters are engaging and appealing. The Student Council president is frigid at first but shows warmth later (and in flashbacks, of course).
Although slightly different, watching this KU first will enhance your enjoyment of Genshiken later if you watch this series first. I went back and re-watched Genshiken after watching this stand-alone series, and I definitely appreciated it more.