Like many here, I have dealt with Maximus Cards before and their service was impeccable. I paid my money and was sent my US PSN code straight away, as they promised.
So, despite them being more expensive than pretty much anybody else that's hawking the US cards, I just purchased another, via Paypal, due to believing from past experience that they are reliable.
Now, they may claim "Instant Email Delivery" of your code upon purchase (it's like a rash all over their site), however from this particular experience it is a complete and utter lie.
Instead, after they took my money – and with no warning beforehand – I was advised by email "Need more data to send code" and demanded to fill in details (including my phone number) at their website. I was then advised they would get back to me within 12 hours.
Instant?! I'm sorry, but "12 hours" and "instant" have no correlation whatsoever. Not to mention the implication that I am in some way shonky, which is certainly not appreciated.
As the heading suggests, beware, for if you want your code "instantly" as Maximus Cards promise, you may be left waiting.
UPDATE: When they finally sent the code through, it didn't work (yes, I tried it several times)...