Interesting thread here. I see 90% of you are from USA, so here's what happens in Italy.
I've been living in Rome since 2008, always in the same northern periphery hood. Most people are here because of lower prices (this is one of the most expensive cities about rent), but they don't "live" the hood or work here.
There's only one giant (for Italian standards) mall that was the start of everything back in 2006/2007, when people started actually living in small flats totally alike inside and outside looking too. Building companies have total control over peripheries, so when I go running sometimes I see popping up new building sites for more houses. Some of these builders are also into politics, so they can do more or less whatever they want. At least half of these apartments are still unsold, so they're just waiting for the city to get bigger and bigger and raise prices also here.
The only comfort is that we're near the ring highway that surrounds all the peripheries of the city, so if you have a car is ok (excluding traffic and crazy fuel prices). Public transportation sucks (and it's expensive too), so if you want to go to the city centre you'll need at least one hour or more.
About security, there's not much to worry about compared to other hoods, but some empty areas are used to leave stolen cars or motorcycles. Foreigners aren't much accepted yet here (Rome generally), we have lots of people from China, Romania, Albania, Morocco, Egypt, Bangladesh and so on, but crime tolerance is high so they're often linked to illegal business. Gypsies are a serious problem, lots of them come here to stay and none of them works. They steal for living, mostly, in all the ways you can imagine, not only against tourists in the city centre.
But it's a good city for metalheads: lots of small/medium venues where you can see bands of any kind, lots of pubs everywhere generally with good beers and food and affordable prices if you don't go to areas that are just "traps for tourists".
Almost needless to say, a ton of art and history testimonies more or less everywhere yo go, inside and outside the city.