I live in a six-floor apartment building in Seattle built above commercial shops and offices. I love it. It's not like you should worry public has access to the building you live in. It'd be like being afraid to go to the grocery store. My apartment building itself is secure access; you have to let youself in using a fob (sort of like a key card at a hotel) which opens the door. There's a narrow spot between all the businesses where the apartment lobby is. I share a common building space with a coffee shop, a sandwich place, a haircutting business, and a Yoga centre. Many other spots in the neighbourhood do the same thing. It's great. Very lovely conveniences. I walk two blocks to work every day, and I typically walk to pick up dinner. We rarely cook and live in a neighbourhood with about a dozen great ethnic restaurants within a one-block radius. I try to incorporate commercial with residential in my SC4 cities, usually sticking commercial on two sides of a road, and have streets branching out from the roads with light residential on the streets, and make another commerce road every five or so blocks. I put MT stops (usually buses) in each commerce block, on each corner, which is every 6 to 8 tiles. Then I usually stick one MT stop for every two residential blocks. If commute traffic gets heavy (normally over 100 or 150 cars going through one area) I change it to a road and put MT stops on each block the road exists. When it's time to switch to middle or dense residential, I do the same. Switch streets to roads, and one MT stop each block. Anyway. I vote YES for urbanism.
