What can I expect flying First Class on American Airlines from US East Coast to Dallas Fort Worth then on to Honolulu Hawaii.
Is it worth the extra money?
It is quite a long trip.

Much more comfortable seats, free drinks and a hot meal. It is definitely nicer than coach and well worth using miles to upgrade but I don't think it is worth the extra $1000+. Of course, it depends on your budget. I'll rather spend that money to upgrade my room in Hawaii.

Unless there is a schedule change, the DFW-HNL is serviced by 763 with the new business class seats. The plane is a 2 class plane that's why the business class is called first on a domestic route. Anyways, you will get a very nice, slightly angled, fully flat seat, nice food/drink service but no IFE, just the big screen for movies.

This flight is almost or just as long as a US-EUR flight so to me it's worth the upgrade but as stated above, it depends on your budget.

If you fly in FC on paid tickets, go here first: http://www.flyertalk.com/forum/showthread.php?t=702660