I agree. I have a 3GS, so I will get more out of iOS4 compared to the 3G, but although I would like to upgrade I realise – exactly like you said – my current phone is such a massive leap from my previous (and the fact I waited until the third generation) means I can let the new iteration pass me by. I am not interested in FaceTime, but the retina display and speed boost will be impressive when I finally upgrade. All the other features are software based – and I get.
Written on my iPhone.