We flew into Belgrade from Tokyo last week. Eleven days in Japan is such a huge bolus of experience that I'm still digesting it, so the ongoing travelblogging will be out of order. (You probably don't care, but this does bug my OCD tendencies a little.) On the other hand, what follows will often mention Japan as a point of contrast.
Japan has a reputation for being a conformist culture, but upon landing in Serbia, one of the first things I noticed was that, to a first approximation, all young Serbian men seem to have the same utilitarian close-cropped haircut, which is a contrast with the carefully styled and sometimes flamboyant male haircuts sported by many young Japanese men. Likewise, Belgrade women's dress is casual and, again compared to Japan, almost drab (which isn't to say that it's drab in an absolute sense), for which I'll advance two tentative hypotheses. First, obviously, Serbia is a dramatically less wealthy and densely developed society. Fewer people can afford to invest extensively in personal ornamentation, and the lower level of economic specialization also leads to fewer opportunities to invest in distinctive fashion. Second, perhaps Japanese women, and especially women in Tokyo and other major Japanese cities, feel more pressure to invest heavily in self-presentation, although I'm unsure whether that's social pressure from peers and acquaintances, or dating market pressure. (Somewhat relatedly, the MR bloggers have a speculated rather extensively about where women are beautiful, but I'm not sure any of their hypotheses explain Japan very well.)
Belgrade is a small, easily digestible city. You can walk around the entirety of Old Belgrade in a day. The museums we visited (Nikola Tesla, Zepter, the Ethnographic Museum) were similarly human-scale. You will never have the feeling, familiar to anyone who has visited the Met or the Louvre, of spending three hours in a museum, being exhausted by the ancient, massive profusion of human culture, and still feeling that you have not even seen the whole museum. Of course, this is because Belgrade's museum collections are much more modest, but that's the tradeoff. (Note that several of Belgrade's major museums have been under renovation for years and are thus currently unvisitable.)
At current exchange rates, everything in Serbia seems cheap by developed-world standards. We stayed in private double room at a hostel in the city center, about three blocks from the National Assembly, for about 4000 RSD (US$47) per night. 1200 RSD (US$14) will buy a fairly extravagant meal, including alcohol, or alternatively will feed you well for a day on more modest fare.
Three days here have hardly made me an expert in Serbian cuisine, but it does remind me of the fact that hot dogs and American megabrews (Budweiser, etc.) are both lineal descendants of central European sausages and lager. Meat and pale yellow beer are the order of the day, and for what it's worth they're done reasonably well. Vegetarians and teetotallers will feel rather deprived. On the other hand, I had some of the best cooked squid I've ever tasted at Cafe Reka in the Zemen district.
There are many, many charming places to relax with a drink. The numerous cafes and bars on the broad pedestrian boulevards, the splavs (cafes, bars, and nightclubs built on river rafts), Skadarlija street, and the Zemen district could all feature as eye-candy backdrops for some terrible formulaic romantic comedy. I'm too old to go clubbing anymore, but Belgradian nightclubs are likewise rumored to be excellent. There is abundant street life everywhere in the central city.
The people are mostly friendly. It is difficult to believe that there are tens of thousands of living war criminals walking among them. I doubt that most Serbians think the war was excusable, but the body politic has certainly not owned up to its guilt. The museum at Petrovaradin Fortress in Novi Sad contains a laughably self-pitying exhibit on the NATO bombing of Novi Sad, without a word about the wider Yugoslav War that prompted it. I can't really do justice to this subject at all, but if I get around to writing about Bosnia, I'll come back to it.
Religion seems to be taken seriously by a wide swath of the populace. Visit an Orthodox church and you will see people of all types (not just what Americans would read as "religious conservative" dress) kissing icons with evident emotion.
Overall, I think that Belgrade in 2013 would be an ideal place to visit if you're about 25 years old, not completely broke but perhaps watching your bank account closely, ideally with a mixed-sex group of five or six friends, one of whom you have an unconsummated crush on. It's cheap, fun, pretty, easily navigable, and frequently romantic, and the lack of top-tier cultural attractions is less important when you're young.