We just returned from the Rotterdam 4/3-13 cruise so I will be able to answer lots of questions with the most up-to-date answers. Pinnacle Grill- don't bother to make any reservations now and if you already have I would cancel and then make them onboard when you know which night(s) you want to go. In fact you will find you don't need any reservations at all- it is almost empty and I walked by there every night on our way in and out of the dining room. At the most we saw only 4 or 5 tables taken on any particular night and most nights it was less than that.
The girl at the Odyssey/Pinnacle reservation desk told me that since they have been charging the $20/person, table bookings have fallen off so dramatically that you can go whenever you want with no problem at all. This was definetely our observation. Most nights only 3 or 4 tables would be taken. On the last formal night we were asked to dine with the Captain and I was seated next to him at his table in the dining room. I brought up the subject of various changes being made on HAL, including the Pinnacle. He said that Odyssey/Pinnacle bookings are down way more than 50% since they started charging and it just wasn't working out as HAL thought, but he didn't think they would go back to a no-charge alternative restaurant even though the $20 charge had not been accepted by passengers. I don't think you can get a better answer than straight from the Captain himself.
We went once, and though it was good, it wouldn't qualify as anything special here in Atlanta, and we do eat out a lot at some of the really good restaurants here, so think I am a pretty good judge. The menu is very nice with a nicer selection than the regular dining room, but we didn't think the food preparation was so outstanding. Three to four stars maybe, certainly not five. Four in our party (our regular dining room table of 6 went as a group) had lamb- all ordered it medium-rare but received it well-done and it was dry. All four were very disappointed. One gentleman ordered the filet mignon and was pleased. I ordered Seafood Cioppino (mussels and clams in tomato sauce with pasta) and it was good, but not memorable. Appetizers and salads were very good and a better selection than in the regular dining room, but I thought the dining room was way below what we had on Celebrity in both these areas, so I did enjoy the Pinnacle for these. For dessert we had Tornado Cake which has been mentioned on one of these HAL message boards and we enjoyed it, but the dessert in the regular dining room is very nice, too (though Tornado Cake is only offered in the Pinnacle). Servers in the Pinnacle seem to think that being upscale means you have to be unfriendly and snooty, which we didn't like and was unnecessary if they thought that was the way to get 4-5 star status. All in all I thought the food in the Pinnacle was better than in the dining room, but not as great as they are trying to promote it as being.
So my comment on the Pinnacle based on personal experience just a few days ago is to try it while you are there, but there is no need to rush to make reservations, certainly not online or even the minute you get on board. Believe me, you can get in ANY night even if you arrive with no reservation. Dining there now seems not to be a priority with most passengers. By the way, Mark and Roger, we were upgraded to a Penthouse during the cruise, so I can answer questions on that, too, for you.