Do NOT get a Sky Suite; it's not necessary. You get a butler (who serves two snacks in the day) and larger cabin & bathroom, but not worth any significant price increase...just get a normal balcony-grade cabin and you'll be fine. Never get a cabin with a window (only) on any ship...not worth the price increase and you get extremely limited "view." Only get either an inside cabin or balcony-grade cabin on any ship.
Weather in Baltic ports (July) is very fickle; take umbrella, shorts, light-jacket, cap. All Europe cities are NOT ADA-compliant...if you have walking difficulty (stairs, cobble-stones, etc.), then you will not be able to go to all sites in any city. I cannot stress this enough, there is significant walking with no accommodation at all sites that is not for the challenged.
Not much to see in Copenhagen (2-night max). Compared to other Europe destinations, you should visit somewhere else; plus, Copenhagen is a very expensive city. Only visit if you are taking a ship to/from. I recommend the "Front Hotel."
In Warnemunde, do NOT take train (un-air-condition) to Berlin. Takes 6-hours round-trip and you are only in Berlin briefly. You should co to Schwerin (sp) and tour Duke's Castle. If on Sunday, do NOT go...just tour Rostock or stay on ship. On Sunday in Schwerin, all shops are closed and castle is not worth train or bus trip. Ship offers excursion to Schwerin, but you can do it by yourself much cheaper and with more freedom by simply buying a ticket at the train station immediately outside the ship...we did.
In Tallinn, you can do your own walk-around tour in this delightful city. Visit Tourist Information (TI) office in city for maps and guide options. A "Tallinn card" may be good deal for you.
Helsinki is not worth getting off the boat. They offer a $12 round-trip shuttle (leaves ever 30-minutes or so), but there is hardly anything to see in the City. If you're bored, take the shuttle to the town-center an walk around...don't get your hopes up.
St. Petersburg is packed full of sights to see. Instead of the ship's excursion (buses), you should go to the Red October website and take a suggested tour (2-6 people). It cost less than a ship's excursion..and much more custom and private. You do NOT need a Russian visa...Red October will handle your clearance, but you must book about two-months in-advance. We did a two-day tour, and it was great. Do not do a evening tour also (ballet or folk-dancing). The day tour is exhausting and you will not feel up to do an evening event too. For the day tour, tell Red October (RO) you want to skip Catherine's Place (spend more time at the Hermitage). Do the Gold Room at the Hermitage. Peterhoff Place was very impressive; make sure you arrive after 11am to see the fountains...very impressive. Tell RO you want to skip the walk through the garden at Peterhoff...if there is other stuff you wanna see elsewhere. Absolutely tell RO that you do NOT want to take a walk after lunch down some major shopping street. It is dangerous, very busy, hot (July), you can't shop because you don't have roubles, and they are just killing time. Again, do NOT take the "shopping walk." There are two stores that they are going to take you to anyway before the walk...so do any shopping there. Also, tell RO that you do NOT want to do lunch at any "chain" restaurant. Understand, RO is a private guide that you hired, tell them what you want and don't want.
Stockholm is a delightful city worth 3-4 nights. Only stay at a hotel near the Palace; such as, Grand Hotel, Radisson, or Sheraton.
Getting a taxi at port in Stockholm is a long wait (1-2 hours). It would be best to pre-reserve a car/driver to pick you up at port...so you avoid the very long lines in the heat and sun. Also, as of July 2007, there is no covered area to stand in for you OR your luggage (which sits in the open waiting for you to pick-up). I suggest carrying ALL your luggage off the ship with you...if you are physically able.
The ship is a very nice ship and you will have no problems on-board.