We just came back off the Harmony and had the Ultimate drinks package and for us it was well worth it as we made our way steadily though the ships various cocktail menus! This was a brilliant side affect of having the package as we tried cocktails we simply would not have done at $11-$13 a go, but when it's included there's no risk. Don't like it, don't drink it, get something else. Although to be honest there were VERY few we didn't like ;)
We didn't have to pay for any drinks on board, except for in the dedicated Starbucks (which was not included, although I thought it was). On other ships, including Quantum, the premium coffees on the Promenade were included but on Harmony the promenade cafe didn't have any premium ones and instead you had to go (and pay) at Starbucks if you really wanted something above the normal coffee. We only went to Starbucks the once!
All of the other usual premium (fresh OJ) and such is included as normal.
As Matt has said on a few podcasts, it really is down to how much you are going to use the package, and of course knowing that you won't have a large drinks bill at the end of the cruise and can just get on with enjoying yourself, and for us this more than makes up for a few $ more.