I fly frequently - to one or two different cities a week. I have elite status with two major airlines. One of the benefits of frequent flying is the upgrade to first or business class.
Here is what I've learned so far as an frequent flyer with elite status:
American Airlines let's elite upgrade for $30 if a seat is available. You can ask the reservation desk to be placed on line (or at the gate). You can also upgrade on-line or at the electronic kiosk. American Airlines automatically awares automatic upgrade certificates every x,xxxx miles - but I have never received any.
United Airlines will often give a complementary upgrade to premier or more frequent flyers, however, it's up to the discretion of the gate attendent and seat availability. Otherwise, you can buy a book of upgrades of four for $200. I've met quite a few obnoxious gate agents who wouldn't gve complementary upgrades. I believe United issues automatic upgrades certificates every x,xxx miles. I have never recieved any.
Due to the uncertainty of availability, it's hard to make a preference either which way. I usually find the $30 upgrade less painful than the $50. I don't mind the $30 if I'm tired and want to sleep or need to work.
I also noticed that more and more American Airlines planes have electric power supplies under the seat - time to break out the ICE power adapter from Radio Shack.
What is your opinion / experience?