Transferring water is a good idea if you're moving the fish. There can be a significant difference in aged tank PH vs fresh tap water. Make sure the temperature is within 1-2f, or you'll need to bag and float the fish.
So long as you're moving EVERYTHING, it should go very smoothly if you don't let anything dry out, or be exposed to water that has not been treated with dechlorinator.
If you're just moving filters, feed VERY lightly for the first few weeks.