Google pulled the location sharing features from Google+ recently, which was annoying because the corresponding feature in Maps was not actually available yet. Well, it turns out Google was only a little behind schedule. Location sharing in Maps appears to be rolling out wide right now.
Location sharing is accessible from the navigation drawer—it's currently marked with a "New" badge. When you fire it up, you can choose to share your location with anyone you pick for any length of time. You can even leave location sharing on indefinitely. Sharing is also accessible by tapping the blue location dot. However you do it, you need to set up sharing even if you had location sharing enabled via the old Google+ method.
When someone shares their location with you, they appear in the bar at the top of the map. Just tap there to see their location. At the bottom of the map you get location information and a handy toggle to share your location back. Plus, Maps has some new home screen shortcuts for seeing shared locations and sharing your own.
Note, shared locations also appear in the main map interface, but you can hide them if you want. If you're sharing your location, you also get a new shortcut button to the share menu on the right side of the screen. It only appears when the map is centered on you, though. Location sharing has shown up for all the accounts we've checked. If it isn't appearing right away, restart the Maps app and look again.