I have noticed that I don't receive messages sent by friends or family to my iphone however I do receive these messages on an ipod or ipad. This can be very frustrating when people need to contact me in a hurry. There are at least two people whose texts I don't receive.
Also, whilst in Spain on the 16 May at 08.11 I sent a text to a friend also in Spain and it was not received by our friend until Thursday evening. It caused a lot of problems as it was changing an appointment so very inconvenient.