Dull, irritating, and not even remotely as funny as it thinks it is.
Let's get Conker's supposed humour out of the way first. Though the game has a few "heh" moments (mostly early on before the humour overstays its welcome) the vast majority of the jokes fall completely flat. Many rely on an overuse of bathroom humour and bad language. Though seeing a cute squirrel use profanity is mildly funny at first, its overuse becomes tiring quickly. This can be said about the bathroom humour as well.
The parodies in the game are pretty weak, and are more references than true parodies. Even in 2001 when this game came out on the N64 the references had already been bone before, done better, and in the case of the Matrix, done to death.
Next is the gameplay. Tedious is probably the best word to describe it. Combat is dull and repetitive, and even when you finally get to use guns near the end, it quickly becomes tiresome. Checkpoints are abundant at times, and then frustratingly absent at others, and with tons of cheap deaths because of one-hit-kills or enemies knocking you off ledges this can get annoying very quickly, especially in certain sequences. Platforming elements are irritating thanks to a horrifically bad camera, a slow-to-react character, and an insanely small distance beyond which Conker will die if he falls.
The useless implementation of lives is annoying thanks to having to wait for some cutscene to load upon losing your lives and subsequently the menu screen, and finally loading the world again. Since saving is done whenever you enter or exit a room and after completing certain tasks, having to reload your last save upon losing all your lives doesn't leave you any worse off than you would be if they just gave you infinite lives.
Conker's plot is weak, and segments are so poorly connected that you frequently have no idea where you're supposed to go next. Ultimately it comes down to trial and error until you figure out where your next task lies or what your next action should be. Charater's voices are horrible, and the attempt to make the characters sound stupid makes them incredibly difficult to understand. Many characters talk so painfully slow that cutscenes become tedious. Several cutscenes are quite long and this makes the slow talking all the more worse.
Several sequences in Conker are mildly entertaining, but on a whole Conker is an incredibly boring and tedious experience. It's thankfully short, taking me about 11 hours or so to complete, but even that was at least 5 hours too long.