I think about 85% of the people will tell you that a balcony is a must. We booked an inside cabin for our cruise next summer for budgetary reasons. There were three things we wanted, but we figured we could only afford two of them; a pre-cruise trip exploring Denali, breathtaking shore excursions, and a balcony to sit and watch the views. We thought the balcony was the least important of the three, because we'll only be in our cabin to do the three S's. Who wants to look at a whale in their underwear anyways? ;-)
So yes, I think a balcony would be cool, but not at the sacrifice of other cool stuff. There are plenty of public places on the ship where you can sit and enjoy the scenery. But if someone gave me the extra cash for the balcony, I wouldn't turn it down.