Hawaiian Airlines: Preferred Seats What it is: Certain bulkhead and exit row seats, plus early boarding and a headset; available only on flights within the U.S. or between Hawaii and the mainland. What it costs: $25 each-way; complimentary to some elite members. How to get this: Available 24 hours before departure on the airline's website, airport kiosk or ticket counter, or at the gate; first come, first served.
JetBlue Airways: Even More Space What it is: More spacious seats in the front of the cabin and exit rows, plus early boarding. What it costs: $10-$65 each-way, depending on route. How to get this: Can be purchased on the airline's website during booking or check-in.
Southwest Airlines: EarlyBird Check-In What is it: A better boarding position which means a better shot at an aisle or window on this "no reserved seating" airline. What it costs: $10 each-way; free to Business Select and elite miles members. How to get this: Available only on Southwest.com when you book your flight.
Spirit Airlines: Big Front Seats What it is: Wider seats in the front of the aircraft with more legroom in a 2X2 configuration; not available on all planes. What it costs: Varies from $12 to $199 per seat depending on route and whether seat is reserved in advance. How to get this: Purchase during or after booking; not available for purchase with miles.
United/Continental Airlines: Economy Plus Seating What it is: Seats with up to 5 inches of extra near the front of the economy cabin; available on all United aircraft and some United Express carriers. The program will be expanded to Continental in 2012. What it costs: Starts at $9 each-way or you can purchase a year's worth of Economy Plus for $425; free to elite miles members. How to get this: Purchase online when booking your ticket or at airport counters, kiosks and gates.
US Airways: ChoiceSeats What it is: Same amount of legroom but toward the front of the cabin; includes earlier boarding; available on all flights except US Airways Shuttle. What it costs: Prices vary depending on length of flight, time of flight and destination; free to elite miles members. How to get this: Available on the airline website or reservations phone from booking through check-in; also available at the airport.
Virgin America: Main Cabin Select What it is: 6 more inches of legroom than main cabin plus priority check-in; free food and drink, too. What it costs: $39, $69 or $129 depending on whether it's a short, medium or long haul flight. How to get this: Book online at up to 24 hours before departure or at the airport or even onboard the plane if available; you can pay a fee to upgrade to First Class as well, up to 6 hours before departure.
Is it worth it? Depends on your tolerance for having someone's coach class seatback in your face (I can cope for a couple of hours, but draw the line at international flights). Check with friends and colleagues to see if they think merchandised or premium economy is a good value or visit your favorite travel chat site (I love the discussions on FlyerTalk). Try a test run; I recommend an outing on a short hop so you won't be spending too much in case it's a dud.