I bought a new iPhone 3G off of Craigslist and it has software version 3.1.2 on it. I know there were issues with the 3G running poorly on iOS 4. My question is has this been resolved in 4.1 or should I keep the phone in 3.1.2. I don't jailbreak or unlock I just want whatever runs best. Also a couple apps I like will not run because of the current firmware version.
It will still run slower on a 3G then any other device (2G and iPod 1st gen excluded) but Apple went through and cut most of the issues (and some features) out of 4.1 for 3G.
You should be fine though,
have fun with your new device.