Because the new iPad is their girlfriend. It's easy to say ditch the girl when you have none of your own.Why are so many people advising that the OP leave his girlfriend? I'm she is worth more to him than an iPad.
I would first ask your girlfriend if it's OK to exchange it.
Do this face to face so you can read her face/body language and tone of voice.
If she says YES but her body language/face/voice says no, I would just keep the iPad2 and return the new iPad. Otherwise, this will be something that may impact future gift purchases or cause drama that may lead to unpleasent alone time.
Of course, if this girls means nothing to you, then do what you will to satisfy your technical gratification.
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You must not understand how a woman perceives giving a well thought out gift.Honestly I do not understand why an adult conversation with the girlfriend would end up in a win win for everyone. What she did was very nice. But given the new iPad launched TODAY, I would expect my wife (sorry, no girlfriend) to understand that while I value her thought, I want the new one. So getting a new one with the same engraving should make everyone happy.
If I could not have had a simple conversation with my (then) girlfriend to arrive at a mutually satisfactory conclusion over something so TRIVIAL, I would not have married her. 50 years of this stuff could get old quick.
Returning a gift that has had some thought behind it because of your own self serving desire would say a lot about your character and relationship.
A good woman is hard to find.
Inanimate objects will come and go & are replaceable.