I tried Premium Class for the (long overdue) first time this week, on a HND-OKA trip with my wife and 1-year-old.

The ground handling at HND is pretty well implemented. There is a special check-in counter for Premium Class which leads directly to an exclusive security checkpoint which leads directly to the lounge entrance. (For ANA Diamonds there is apparently a separate and even swankier check-in and lounge arrangement.) My only real complaint is that they still don't have any food in the domestic lounges other than snack mix. OTOH, the lounge in OKA had Orion beer and coffee awamori liqueur, which were interesting local touches.

Premium class and *G get priority boarding together, after passengers traveling with small children (so for us this wasn't really an advantage).

The seats vary somewhat between aircraft models. We flew 777 one way and 747 the other way. IMO, the 747 is the way to go if you want the full premium experience: the seats have a wing-back design which gives a greater feeling of privacy, and there are three single seats for those who want even more personal space (two in the nose and one "Captain Kirk" seat in dead center of the cabin) -- caveat being that none of these seats have their own overhead storage space so you might end up having to steal someone else's. ANA premium class must be one of the cheapest ways out there to buy a ticket in the nose of a 747...

Beverages are complimentary and free-flowing. The menu is worthy of an international business class product, with red/white/sparkling wine, several liquors, Starbucks coffee, Perrier and a bunch of other options that are not available in the main cabin. The food is a nicely presented Japanese meal, and since it is securely boxed you can take it with you to eat later (they even give you a bag for this purpose).

As usual, ANA rocks when traveling with kids. They gave us a stuffed airplane toy in each direction. (On a longhaul last year we scored a plastic 787 model which now sits on my desk.)

IME, it is always a major crap shoot as to whether you will get offered the premium class upgrade at check-in. I have *never* been offered it even once when flying to/from HND. For this trip I simply paid the premium fare -- premium was sold out on both of our flights when we checked in, but was still open on some others. It may be easier to score the premium upgrade if you check in very early, or from NRT or KIX as everyone is connecting into Y, but I would not count on it when flying between domestic airports.