NEW YORK (FORTUNE) - Admit it. You always have a twinge of envy when you board a plane and have to shuffle past those folks sitting up front. They're already settled and have a drink in their hand.

But next time, look a little closer: what do they really have that you don't? The answer, at least flying domestically, is not much. "People get on the plane and are like, 'this is first class?'" says Susan Daimler of seatguru.com. "It's often a disappointing experience."

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For starters, expect an average of only about 38 inches of seat pitch, or the distance from the back of one seat to back of the next. That's only four or five inches more than most coach cabins. (Internationally, expect at least 60 inches.)

There are no in-seat TVs or on-demand movies. And the food, well, let's just say, at least it's free.

More than 3 million people flew first class year -- in seats that average about $1,100 round trip. Of course, only about 30 percent of them actually paid full fare for those seats. "It's come down to becoming just a perk for frequent flyers," says Steven Casley of BACK Aviation Solutions, an industry consulting firm.

But it's a perk that airlines are starting to realize their most important travelers care about. That's why American is installing lie-flat seats for business-class passengers between New York and Los Angeles. And why United is expanding its "ps" or premium service on the transcontinental routes.

With that in mind, FORTUNE surveyed the domestic fleet.

The best deal in domestic business class. Starting at $35 more than a coach ticket, you get a leather seat with 37 inches of pitch. Sure you don't get any fancy meal but you do get free alcoholic beverages and a snack of your choice. But for the price, it's hard to complain.

If you're traveling between New York and Los Angeles, American's "Flagship Service" is right on the money. The specially outfitted Boeing 767s have nine luxury lie-flat sleeper seats similar to what you might find on American's international flights.

Passengers get Bose noise canceling headsets and specialty menus that can include beef filet with miso demi-glace and cilantro potatoes. (On those flights, there's also a business class cabin with leather seats with a 52-inch pitch. American says it plans to start replacing those seats with lie-flat ones this year.) The rest of the American fleet has traditional leather first class seats with a respectable 38 inches of pitch.

Though Continental is considered to have the best overall customer service among full service U.S. carriers, its domestic first class product is nothing remarkable. Like with other carriers, there's priority boarding, better food (Creole jambalaya or beef tips with bordelaise sauce are some highlights) and bigger seats with 38 inches of pitch, but there's not a whole lot else.

Delta says it's in the midst of revamping their entire fleet with newer seats and wood-paneled lavatories. But it's unclear how fast it will get done with the company in bankruptcy protection. Today expect a respectable 38 inches of seat pitch, access to some Crown Room lounges and full meal service.

But keep your eye out when they start revamping their Song fleet with first class seats -- at least then you'll have live television.

Two words: Avoid DC-9s. On those old planes, you only get 34 inches of pitch (JetBlue offers the same in coach). Not that the rest of the fleet is much better -- the maximum you'll find is likely a measly 36 inches.

You'll still get food on flights longer than three hours, priority boarding and free alcoholic beverages. But you won't get any extra perks like power ports -- they're only on the international fleet.

The airline's ps service, offered between New York, Los Angeles and San Francisco, is the best domestic first class experience. Period. Expect huge lie-flat seats in first with 68 inches of pitch. (Even business class has 58 inches of pitch -- more than any other airline's first-class product.)

Even better, expect treats like bellinis made with fresh peach puree and a "decadent chocolate surprise" before landing. The rest of the United fleet has traditional leather first-class seats with a respectable 38 inches of pitch.

Thank the travel gods for America West. Until they merged a couple months ago, your $1,000 for first class got you only a snack box and a Coke. Now expect 38 inches of seat pitch and food on all flights including items like chicken cordon bleu with California Pasta salad.

A final tip to consider when deciding whether to cash in your frequent-flyer miles. Always check what kind of plane you're going to be flying. Wide body jets like the Boeing 767 or 777 tend to be the best along with any Airbus (they're wider planes). Avoid DC-9s, MD-80s (American calls them Super 80s) or most 737s. It's also worth asking if any of the carrier's international fleet might be flying on your route -- that way you get the best seats. Check www.seatguru.com for the best seats on each carrier's planes.