Speed:
All Standdard apps work on this iPhone flawlessly! Even movies are easily playable. Of course: we compare it with the current models, then you realize that some things can obviously go faster. But it seems by no means complacent.
Camera:
The camera incl. Video function triggers indoors in dim lighting to its limits, for outside it just fine and gives very good results.
Siri & FaceTime:
From a hardware perspective, the iPhone 3 GS can indeed boast neither Siri nor with FaceTime - but who really needs it? Cute gimmicks that you once tried and can have its practical benefits, but they are soon forgotten and they do not really missed.
Display:
The display is not Retina, but all sites are easily readable with healthy eyes - may have to enlarge the text times. Compared to other models in this category Apple had already done with the display Excellent and was thus well above the standard.
Conclusion:
Still an excellent smartphone. As entry-level model in the iPhone world, or as an emergency device highly recommended!