Our cats are always behind the door when we come in. I've learned not to open it too quickly for fear of squishing them. They take a moment (or two if I've been at the shelter) to sniff our shoes, then they scamper off and have a go at the scratching post. Sometimes they'll trot into the bathroom, which is right off the entry, and hop into the tub and ask for water.
It's funny - they know when it's us coming out of the elevator and when it's someone else. I'll be in the apartment waiting for my boyfriend to come home, and other people will come and go but they know it's him the minute the elevator door opens and they go running.