I Fell for the iPhone trap. It finally came available for Sprint users and 3g has never been usable. Completely dissatisfied.
Both my wife and I have had iPhones for the past year and have never had reasonable usage of applications requiring data if we are away from wifi. All of the features I purchased the iPhone for are practically unusable. GPS navigation is too slow to safely follow in traffic, turn by turn directions come to late to make a turn. Siri or any app with other voice operation (voice to text for instance) are almost always non functional. Web browsing is impossible (screen saver engages before a page can load). Photo sharing is very slow and occassionally fails, video sharing will never work at all. And streaming music has never been possible (several different apps have been tried) due to frequent breaks in the music stream (approx every 15 seconds). Application updates fail, ebay auctions will be lost. Weather radar is extremely beneficial at my job, but is unusable away from wifi.
I have performed all system updates, regularly restart the phone, battery is always charged, PRL is current (as far as I know) at 51090. I have friends with iPhone 4S's on AT&T that have had little to no problems with data usability.
There is simply no benefit to owning an iPhone 4S on Sprint. The 3G network will not provide the service as described in Sprint advertisements. My previous phone, EVO 4G was 50 times faster, no exageration. Ive made complaint after complaint for the last year, hearing the same lies of 4G LTE upgrades eventually providing less congested 3G networks. I have received several "discounts" off my bill due to the limited data functionality due to my complaints. But I have come to the conclusion that its never enough of a discount to be worth the hour long phone call once a month to customer support it takes to get to that point.
I truely believe it will take at least another year (if ever) for 3G to become usable. By that time my contract will be over and I will be ending my service with Sprint after 6 years. Until then, I am held to a contract that charges me a "Premium Data" fee for at least 3 of the 4 phone lines I have on contract that is unusable as advertised. The 4th phone is an Evo 4G LTE and seems to work fine most of the time.
Take a look at the speed test and see for yourself. I can provide many more, taken in several different locations all over town with similar results.