Google has released Google Maps 5.7 for Android. You can download it now from the Android Market (Android 2.1+ is required). The new version includes Transit Navigation beta, updated access to directions, better suggested search results, and a photo viewer to Place pages.
Transit Navigation beta helps you figure out how to use public transit directions in 400+ cities around the globe. Transit Navigation uses GPS (so it's only really useful for above-ground transit) to determine your current location along your route and alerts you when it's time to get off or make a transfer.
After starting your trip with Transit Navigation, you can open another app or put your phone away entirely and Google Maps will still display an alert in your notification bar and vibrate your phone when your stop is coming up. This is particularly helpful if you're in a city where you don't speak the language and can't read the route maps or understand the announcements, but it can also be used for those that are directionally challenged or are just too lazy to pay attention to where they are going.
Google has made it easier to access directions: if you select the driving or walking icon and your route is supported by Google Maps Navigation, the Navigation icon will automatically appear so you can access step-by-step directions (this doesn't work for public transit). Before, clicking directions in a Place page would bring up options for Driving Navigation, Walking Navigation, and Directions, but now, you'll be taken straight to the map with the new directions box.
Google has improved the quality and speed of search suggestions by adding category icons to reflect the type of result (a pin for a Google Places listing, a star for a starred Place or location, a clock for a previously used search term, a person for contacts, and a magnifying glass for anything else). Last but not least, Google has added a photo viewer for Place pages so you can browse photos while deciding where to go.
I would argue that Transit Navigation is the most important part of this update, but that's because I regularly use public transit. Still, the rest of the improvements seem like minor touch ups, though of course they're still welcome.