Yes, I did it. I should know better, right? I mean, I lived in New York for a time, and grew up a bridge-and-tunnel kid. It's the most touristy spot in the world, right? Well, I'm thirty-mumble years old and I'd never been, and I was staying practically behind it, so more for the benefit of the tourists than the locals, here's a write-up on the Carnegie Deli (7th Av. at 55th St.).
First off, don't order at the counter unless it's to go. The back is waiter service only. This means that at some point a waiter will stop at your table and stare at you. This is your only cue to speak. I heard some people with really obviously Minnesotan accents talking about "wow, they weren't kidding about people in New York." This is not representative of anything except servers in touristy restaurants everywhere. The same behaviour can be observed on the Champs Elysees, La Rambla, the Ponte Vecchio, Third Street Promenade or Pier 39.
What this means is that you cannot buy a sandwich at the front, take it to the back, and eat it. Waiter service only.
My suggestion? If you're there because you really want good New York deli, walk out the front into Seventh Avenue, put your hand up, hail a cab and go to Katz's on East Houston Street (and remember that it's "how-stin" not "hue-stin"). If you're there because you can't deal with taking the F train to someplace better (Katz's), but you don't want to be treated like a particularly ugly insect, get it to go and walk up Seventh Avenue and eat in the park. If you're there because your Aunt Edna from Saskatoon told you it was a seminal New York experience, go ahead and sit in the back and get waiter service.
The food -- deli sandwiches are fine. The corned beef is actually quite good; the pastrami ditto. The rye bread is completely insipid and will be mush by the time the sandwich hits your mouth because of the sheer volume of meat on there. The hot food (potato pancakes, etc.) is just... meh. Desserts are OK but large enough to be shared by a party of six (and priced that way, too). The half sour pickles are OK; the full sour pickles are chaloshes (that's Yiddish for "gross", by the way). The sour green tomatoes are OK but not worth $3 extra.
Prices are high. Expect to pay $10-$20 for your sandwich. Granted, it's a shamefully large amount of meat, but it's still a lot to pay for a sandwich that comes with four forlorn little pickles in a plastic cup. A pastrami sandwich is $14. The chicken salad with bacon and half a friggin' head of iceberg that a friend ordered is $21.
Service is damn near nonexistent. You will have to essentially physically stop your server in order to get anything (napkins, silverware) that you didn't order when they first graced you with their awesome presence.
It's cash only. That's right -- no checks, no credit cards, cash ONLY. So stop off at the ATM on your way to get ripped off. Don't overtip. You were treated badly -- everyone is treated badly. You can tell why by listening to the accents in the room -- foreign, Southern and Midwestern. So don't overtip, do you want to encourage this sort of behaviour?
In conclusion: if you're looking for the best deli in Manhattan, this isn't it. If you're looking for a reason to convince Aunt Edna to slum it down to the Lower East Side, you've got a better chance. If you're looking because Aunt Edna won't be convinced, you absolutely have to go -- get a corned beef sandwich and some extra rye bread, and share it with a couple other people.
I will say this: the Carnegie Deli is the very best Jewish-style (notice I didn't say Jewish -- they serve bacon at the Carnegie) deli on the west side of Seventh Avenue between 54th and 56th Streets.