There aren't many anime I would watch in public without hesitation. Humanity has Declined is probably the only one. The art is amazing, the jokes are fantastic.. it's a great anime, although extremely weird. Do note though that it wasn't aired in chronological order; the episodes are out of order, like the Melancholy of Haruhi Suzumiya was. So if you want them to make more sense, you need to find out the chronological order yourself, and watch them in that order. Depends on what experience you want, really; it's a lot more mysterious and weird if you watch it in the order it was aired in.