Apart from a more spacious, less cluttered design, the new contacts page sports three major improvements. Most prominent -- and most immediately useful -- is a deduplication function, where redundant contacts can be folded into each other without losing data.
Duplicate contacts can be merged individually, one person at a time, or all contacts in an account can be deduplicated at once. Both actions can be undone, but there's only one level of undo. If you merge one person's contacts, then merge everything, then perform an undo, it'll undo all the merges performed in the second operation but not the first individual merge. (Some contact managers in Android have a similar function, but it doesn't appear to be implemented consistently between editions of Android.)
Users can also keep contacts up to date automatically. Google claims this is done by "blending your contact's Google profile information with the stuff you already have." Ideally this shouldn't affect contacts that have details composited from multiple -- that is, non-Google -- sources. Last, Google provides links to the most recent conversations or meetings with a given user from that person's contacts card.
The revised Contacts page seems pitched mainly at regular users, not the business-class customers Google is attempting to woo through Google for Work. Still, the company may be aiming for a sweet spot between its business and personal users; decluttering one's contact list, for instance, is a feature both groups would appreciate.
Google plans to add the new contacts pane to Gmail "over the next few weeks."