My Nokia was too old to go on the internet so I decided to buy an iPhone which had the advantage that I could take my iTunes music with me and have it all in-one. I went for a refurbished iPhone 3G because, first, I didn't need (or could afford the latest and the 3G was sufficient for my needs) and, second getting a refurbished one meant it had been checked over which simply buying one on ebay wouldn't necessarily have been the case. The sellers had a plenty of good feedback so I was happy to buy from them. I bought an O2 phone and this meant I was able to transfer my sim card from my Nokia with no bother. My only criticism (which isn't limited to the iPhone but applies to nearly everything, even new) is that you don't get a user's guide but I was able to download it from Apple's website to set it up and get to grips with all the apps on it.
I am very impressed with it. It does everything I want and I've had no problems at all. I would admit that using the touch pad keys takes a little getting used to but you soon get the hang of it. I was also impressed with the sellers' service.