The Core is notable in that the writing quality improves markedly as the story goes on, while at the same time the gratuity level goes up as well. Thus, it gets easier to read as a piece of literature, and, for some people, harder to read as a piece of literature, at the same time. If you don't mind the style and you're something of an otaku, it's worth reading. Even if you think DirtyPair refers to something you should put in the laundry basket, the first episode has quite a number of general college life comments which might be amusing (especially for CS people...).
The anime on which the 'fic is mostly based is Dirty Pair. The title "Undocumented Features" refers to the interesting undocumented feature of the rather bizarre compiler which Gryphon inadvertently discovers at the beginning of the story: the compiler itself has the ability to create objects which have physical reality (guns, motorbikes, power armor, as well as various other things which they don't, but could, use it to create). According to the documentation, one should never compile anything without the -i flag, for "inanimate". The fact that compiling without -i works at all is the undocumented feature referred to in the title, and makes Kei and Yuri the title characters.
Other sources used for characters, equipment, and situations: Star Trek, Star Wars, Battlestar Galactica, Tigers of Terra, TenchiMuyo?!, Ninja High School, Silbuster, the Transformers, Star Trekker: the Manga Parody, the Vorkosigan novels, Goldfish Warning!, Robotech/Macross?, Iczer-One, Star Wars: the Roleplaying Game, Appleseed, Space Battleship Yamato/StarBlazers?, the Legend of Zelda, Outlanders, Wing Commander, Gold Digger, the Honor Harrington novels, Frank Herbert's Dune, BubbleGumCrisis?, and ManyOthers.
If you managed to make it through UF and could take the gratuity, and you're a NeonGenesisEvangelion fan, highly recommended is NeonExodusEvangelion, also written by the Eyrie crew. It's not a self-insert (well, not mostly; Truss is SI). It's not a MegaCrossover (...mostly...). But some of the characters are extremely silly. That said, it's written to be taken seriously (I think); if you can't take that, read it as a spoof. 'sgood. (And check out the Angelspotting poster, either on the site or on JustinPavas node But why on earth would I want to do that?).
Part one of the core just hosed the first 5 hours of my work day. --Joe Mwahaha...
PresidentStrauss? gets about five seconds of screen time in part one of the Core (he was at WPI when this was written).
The one-question geek test should also be mentioned here: according to the Jargon Dictionary (http://info.astrian.net/jargon), "You say to someone 'I saw a Volkswagen Beetle today with a vanity license plate that read FEATURE'. If he/she laughs, he/she is a geek."