What is the best option for upgrading my iTouch 3g to iOS 4.0 while keeping my jailbreak?

Upgrade and re-jailbreak.

Don’t bother upgrading your iPhone 3G to iOS4. It totally screws up your phone. It slows down to a crawl. I upgraded mine and now it’s a horrible experience. And you can’t downgrade to 3.1. But I did figure out a little trick that solves the problem a bit. Turn off spotlight search and it works a bit better.

@Mtl_zack I thought they (techies) had figured out a way around the need to “call home” for a downgrade authorization.

@papayalily well ya, anything can be done by jailbreaking. But it’s not the same as the original. Also, jailbroken phones often run slower as the processor can’t handle things it wasn’t meant to.

I went ahead and upgraded it then jailbroke it, and it runs perfectly fine, but another issue I ran into is that most apps haven’t been updated for 4.0. I’m considering downgrading back to 3.1.3.