A Dynamo huib will feel "notchy" and a bit draggy even with perfectly adjusted wheel bearings due to the permanent magnets used in the dynamo portion of the hub. Peter White Cycles has a discussion of this in regards to the German SON hub on their web site with a warning to NOT try to mess with the bearing adjustment on it as they are non adjustable sealed cartridge bearings. Trying to do so can break the wires to the electrical connector on the hub.