A transformer winding is generally more inductive than resistive thus there is a considerable phase difference between voltage and current, so wouldn't the supply power factor be very very poor in case of residential transformers where no means for power factor corrections are used?
Unloaded transformers look like inductors. However, a resistive load on the secondary makes the primary look more resistive too. For any decent transformer, the primary looks mostly resistive when the secondary is loaded with a resistance near the power limit of the transformer.
So the power factor is very poor when a transformer is drawing little power, and gets better as the power increases. Fortunately, you care more about the power factor at high power levels.
All that said, the grid does generally look partially inductive. Large industrial motors generally present a more inductive power factor than that added by typical transformers.
Large electric customers that pay extra for a low power factor usually have a system of compensating for the inductive power factor. This is usually banks of capacitors that are switched across the power line to cancel out the inductance.