The iPhone 4 is still a decent phone. I am still using that because I'm w-a-i-t-i-n-g for my iPhone 5 to arrive. I have iOS 6 on my 4 and I have not had any issues with it being sluggish. There are a few bugs but I think that's from the OS itself and not due to it being on the 4. It's still plenty capable! However, it's already two generations behind. While it probably will get the next round of big software updates (like the 3GS now), it is going to be unsupported very soon. I would recommend the 4S if the 5 is out of question, but if your friend needs it to be free...well, you have your answer.
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The iPhone 4 is still a decent phone. I am still using that because I'm w-a-i-t-i-n-g for my iPhone 5 to arrive. I have iOS 6 on my 4 and I have not had any issues with it being sluggish. There are a few bugs but I think that's from the OS itself and not due to it being on the 4. It's still plenty capable! However, it's already two generations behind. While it probably will get the next round of big software updates (like the 3GS now), it is going to be unsupported very soon. I would recommend the 4S if the 5 is out of question, but if your friend needs it to be free...well, you have your answer.