We chose to upgrade to business class on Air Tahiti Nui and weren't disappointed. At the time we went, there was no option for first class, but that may have changed.
On the trip out we were on an older Airbus. The seats were fairly nice, but not quite up to modern international business class. The plane was showing some of its age through tray tables that didn't fit right, worn upholstery, etc. However, the seats were comfortable and spacious. The entertainment system was basic and provided what we needed. The food and service was excellent. Overall a very positive experience.
This was even better. This flight was on a much newer Airbus with new international business-class seats. This also meant a full entertainment system (video games, etc). The seats went further back, were more comfortable, and there was more spacing. The food and service was the same, excellent, but the seating made it even better.
For $2000/each it was worth the upgrade on an eight and a half hour flight