I am Executive Platinum on American. I fly business class a lot, and have been able to get first class upgrades pretty easily. The first class product is very similar to business class - just slightly "fancier" food. I actually prefer the business class seat on AA's long haul flights (way more storage space for ipad, headphones, etc. - at the cost of a slightly narrower seat).

The trick to getting most upgrades from business to first is to request the upgrade as soon as you book the biz class flight. You're not likely to get it if you try to do it at the airport.