Immediate, not that much ... You'll have to enter your card code even if it is already registered, the website appears more "it should take less than a minute" and you then announced "we will send you mail under 4 hours with the code ". (Definitely an excess of zeal side security) Personally it took me about 15 minutes.
In short very convenient for different amounts of purchases you can not find in stores and to avoid returning his card on the psn.
