We flew round trip in Economy Plus. They claim to have one of the best such classes and it was certainly better than our usual United; however be prepared for a stiff fee if you want advance seat selection in any class.
World Traveler Plus offers seats almost as wide as business class (most US carriers just offer more leg room and little else) and generous pitch however do not expect to lie down. It has its own separate cabin, but it is still economy so does not offer lounge access or early boarding.
Meals were well served,but not especially fancy, They were superior to economy coach as was the service level. Entertainment screens and system were upgrades from economy as well.
Since an upgrade to business class was $500 pp each way, this is a good compromise for a long flight and definitely more comfortable. The cabin was 2-4-2 seating and we paid for seat selection and took the 2. Bulkhead has more generous leg room.