The reason why people use Western Union is because the transfer is almost immediate. You do not really need to wait for payment. I think it may take more time finding your way down to a Western Union branch
You are right eddy that Western Union delivers money almost immediately but its more expensive compare to other money trnasfer service IMO.
Well, it doesn't matter if it is more expensive. If you are overseas and out of cash and you need to need money fast to pay for food, being able to get the money fast is most important. I don't expect people to use Western Union on a regular basis but just for emergency money.
WU is very instant and it wont take much time and whenever I use it I found it better then any other service, maximum it took 2 hours to get the money for me.
Please refer to WU's website at http://www.westernunion.com/info/faqIndex.asp . You will find your answers there.