I'll try and keep this short and to-the-point. Our cruise aboard the Jade was quite enjoyable, considering our intent, which was to treat the ship as a floating Hyatt or Hilton, that just happened to dock at interesting places. The Freestyle concept works well in this instance, as does the general casual nature of the cruise line itself. If you're looking for a luxury cruise, Jade isn't for you, i'd suspect, although perhaps the suite experience changes the dynamic (which begs the question, why go to Europe in the first place if your entire time is spent in the cabin?)
We booked an inside cabin, which was quite large at around 150 square feet. We never felt cramped, and never had a moment wishing for a window. The space is remarkably well organized, and the bathroom is flat-out cavernous for a cruise ship. Considering how close you are to decks that overlook the sea, it's foolish to spend on a balcony, especially if the purpose of the cruise is not "rest and relaxation" but "discovery and exploration."
We bought their $50 soda program. I highly advise on doing so, in that you'll easily drink its worth in 3 days.
Well planned space. Great, spacious cruise bathroom. Clever use of mirrors to enlarge the space. Who needs a balcony?