My review after a few hours of heavy use on my iPhone 3G with iOS 4.1: Cliff Notes: Phone is the fastest it have ever been, even faster than when it had OS 3.x!!!! I was very very reluctant to update to 4.1 this morning. My reasoning for doing so was this: It's already unusably slow, and barely able to run anything, so the worst that can happen is it stops working altogether. Well after I installed 4.1, I reboot the phone and started to use it. Now with 4.0.1, everything was scary slow - e-mail took 30+ seconds to load, web browsing took minutes to load a page and it would freeze often, the iPod took well over a minute to load, etc... Right now, everything is very very quick. Well, it's an iPhone 3G, so for the hardware it has - it's very quick. Text messages take about 3 seconds to load now, e-mail opens right up, web browsing is a significantly improved. The web browsing is a whole new experience compared to what I been dealing with all summer. The browser loads up in 3-5 seconds, the page doesn't try to automatically reload, browsing webpages is smooth without any freezing, and everything moves without any lagging and very fluid. The iPod takes about 6-10 seconds to load up fully. Not bad compared to before, when it took 45+ seconds and would crash often when it would try to load. Text messaging is another very smooth experience after it loads, there is no waiting after the initial application launch. The camera takes about 15-20 seconds to load and become ready to take a photo. A little better than before, but certainly won't be the best choice if you want to capture something very quickly. Switching between applications quickly is very quick, applications load within a couple of seconds, and are nothing is crashing or freezing. The whole UI experience is much much more fluid than before. Applications load, Mail launches quickly, text messages can be sent quickly, typing text is instantaneous without any sign of lag, all of the buttons respond the first time you press then and actually do what they were programmed to do. All of the horrible nightmares that came to the iPhone 3G have been completely erased with this new iOS 4.1 update. I am going to say that my phone now is actually FASTER than when it had iOS 3.x on it. If you have an iPhone 3G and your phone is a disaster with iOS 4.0.x, I highly highly recommend the upgrade to 4.1. It was most certainly worth the cost of losing my jailbreak and all the applications I had when downloaded when it was jailbroken.