Haha, I know many people who are debating about buying the 16GB, 32GB, and 64GB versions. So, I'm just going to make thing simple here.
16GB - For someone like me who's not a media-centric person, there's just no need for a larger capacity phone. Some may say, just buy a larger capacity phone 'just to be safe' but bear in mind, when you buy the iPhone 4S with a larger capacity, you're paying for it. It doesn't come free, and if you don't use it then that's just money wasted. From a financial and economic perspective, that's just wastage, and wastage isn't good. So, if you don't keep much music and video's on your phone, then you're fine. Apps and other things will not take up even 10GB of data, so don't worry about it.
32GB - This is for people who download about 5K songs on to their phone, regardless of whether they listen to it or not. They also save a ton of HD videos on their phone too. I've never understood storing HD movies on a phone. I mean HD movies are s'posed to be watched on a large screen HDTV. Saving it in a phone is just waste. Other than that, if you like to store lotsa music and capture lotsa videos in HD then this might be the one for you.
64GB - I'm not sure why Apple even made a 64GB phone cuz I think this is just too much. This capacity is for 1) people who literally transfer a bunchof their media on their PC to their phone.
2) People who got too much money, and don't know what to do with it.
So, there you go. A lil guide to those who may be confused or unsure about which phone they want. Also, don't forget there's now iCloud where you can store your pics and songs, so no worries guys..
It's all good

i am buying 16GB too with contract free dont mind waiting after 16th..see you guys here got wat to feedback me. that's why i said 16GB enuf or not...when i said that coz ppl here buying at least 32GB...mostly la.