I've flown on that flight from LAX-PPT (and back) on TN, using AA miles, and it is a great experience, for what its worth. The staff is excellent, and they have very comfortable newer planes with good in-flight entertainment and service.

TN does not assign seating until you reach the airport, so if you get to LAX (or PPT) extra early, you can get yourself a bulkhead or exit row seat pretty easily. I don't remember how early they start taking check-ins, but I do remember sitting in line outside the ticket counter in PPT before they opened for our flight, to make sure we got bulk head seats, and we got them no problem. I personally would not upgrade to biz class myself knowing that you can get exit or bulkhead seats as long as you are willing to get their early, but to each his own.

What island are you planning on going to and what hotel? I can't say enough good things about the Hilton Moorea Lagoon and Spa (was the Sheraton when I was there and used SPG points) if you stay on Moorea for a night or more.