If you use tap water you will in short time have a layer of calcium deposited on your coils. Unless your water is very soft. Some window units spray the condensated water back on the coils with the rim of the fan but condesated water is essentially distilled water so there should be no calcium build up.
my brand new LG unit does this, they even explain it in the manual, several times ... they instruct to install the AC level so water can build up in a storage area near the rear coils ... when the fan comes on, a special rim on the fan picks up water and sprays it on the coils... they call it a slinger fan.