In order for humans not to be disoriented (dizzy) from the rotation, a rotating structure must have a cycle time (complete rotation) at
at least one minute. In order to get 1 g of acceleration in a 1 minute rotation time you need: 33 feet per second * 60 seconds = a wheel 1980 feet in circumference. (approximately 650 feet across) Since any 'upper' decks within that radius will have correspondingly less g, they'll have to be 'storage and utility space' and only decks that far out or farther will be regularly inhabited. So you'll need pretty large ships for a 'routine' 1 g environment. I suspect that
colonies will eventually be built that have this level of gravity but I doubt that many moving ships will.
The balance factor is another sticky problem but I suppose it's more solveable than the sheer size requirements. In order to rotate effectively the ship/structure will have to be relatively balanced, but of course it will never be
perfectly balanced. Various controls can be used, including thrusters and internal movement of material, like stored water or other fluids. Even with computer controlled pumps moving fluids around you can't have a response time or a margin of error that can handle humans running around doing their daily business. Another reason that rotating
ships will probably be impractical but colonies will be important enough to deal with the problems.
