we flew on Song JFK-MCO the first week of June.
they haven't completely finished with their new planes yet, so the plane on the way there had the Song interior ready, but the exterior was still the old Delta design. the plane back was Song decorated inside and out.
anyway, yes the seats are
slightly more comfortable than normal coach seating. nice leather seats.
very colorful interior design, heh.
there was some glitch with our reservation, so we weren't able to print out our boarding passes at home.
when we got to the Song terminal at JFK, we were confused at first about where their check-in area is. you have to walk a fairly long distance and turn around the corner.
that's when you see the empty check-in area w/ absolutely no lines, and a row of pretty shiny new check-in kiosks.

just insert your Delta Skymiles card or the credit card you used to book your flights, and then you can check-in, print boarding passes, etc.
Song's gate area at JFK could use some better food options. there was a fast-food chinese place, and a tiny bakery place. that's it.
the boarding zones do seem to go from front to back of the plane, but i'm not positive that it's as simple a pattern as that.
since Song is all coach class, i believe the first people that board are the ones that are seated in that section which in regular airlines is considered First class.
Song has not yet completed installing their individual TVs for each seat yet. instead, on our flights, they had a limited number of Game Boy Advances that passengers could borrow for the duration of the flight. preference was given to children first, and then any adults who wanted one could request one.
food/beverage Menus are distributed at the beginning of the flight, and there were things like Cinnabon for breakfast, sandwiches (provided by Pizzeria Uno's?) for lunch and dinner, chips/snacks, and liquor etc.
the only things that are still free are regular drinks such as Coffee, Tea, or Coca-Cola products such as some juices and sodas.
i do have to agree with one of the earlier comments on this thread that Song is
trying way too hard to be "hip" and "cool".
it wasn't so bad on our flight down.
but the return flight, there was this annoying flight attendant who thought she was so funny, but she had the most horrible comic timing. the flight attendants kept cracking jokes (like dumb blonde jokes) at each other, and making fun of each other.
plus there was this overly forceful intro at the beginning.
something like, "Welcome on board Song. Let me introduce you to some new terms you'll be hearing. This is no longer considered a flight; it's an EXPERIENCE! And you are not passengers, or customers, you are our GUESTS! And we are not called flight attendants, or stewardesses anymore; we are called TALENTS!"
i mean, we're all Disney fans here, and we understand about how Disney calls us "Guests", and Disney staff are called "Cast Members" etc. but Disney never FORCES that stuff on us.
sheesh.
anyway, besides their trying too hard thing, our experience with Song (pun intended

) was pretty good.
if anyone has any questions, please feel free to ask.
hope this helps!