Well, the main draw is that it's a relatively affluent and safe neighborhood with very good schools. Arcadia High recently just blew $10 million to renovate its Performing Arts Center, like it was nothing. It was funded through property taxes, and no one even batted an eye at the expenditure because there's so much money in the area.
I mean in general. Again, though, I think it's tied to money. White, Asian, black, Hispanic, and anyone else living around the area is generally well off and well educated.
I'm personally afraid of where the real estate prices will be in 10 years. It just continues to go up and up and up, and we've been seeing $10+ million houses show up fairly recently. My house is actually in an unincorporated area, so it's significantly cheaper, but my wife and I are already thinking about how to get in soon so we don't get destroyed by rising real estate values. The problem is the sudden influx of rich Chinese immigrants and nationals, who buy up the houses, tear them down, and build McMansions. At least in Arcadia, the make up of the city has been changing in recent years, since the people who used to live here sold their houses for extraordinary profit (for example, my mom bought her house for like $300K in the 90s, and now it's worth $1.7 million) after their kids graduated and moved to nearby areas that are still nice but cheaper. This leads into...
...bad Asian drivers. I think it's not necessarily that they're bad, per se, but rather a lot of people drive as if they're still in Asia, where traffic laws are a lot more relaxed.