We reported last week that iOS 4.1 was rumored to fix the iPhone 3G's issues with iOS 4.0. Well, after some testing this weekend, I can confirm that the iPhone 3G is now usable with iOS 4.
Since iOS 4.1 is not yet shipping, we had to install it on a developer phone. That said, the developer phone should function exactly the same way as the final OS, with the final working even better since this is still beta 3 of iOS 4.1.
As for what works now, we specifically tested sending and receiving e-mails in the background, while performing some other tasks, like browsing the web. We also used multiple browser windows, searched and installed from the App Store, and set up a new Exchange account (with Google Sync instead). Basically, we tried to configure the iPhone 3G exactly the same way that we use the iPhone 4. I'm happy to report that after using it for an extended amount of time, I can say with confidence that Apple has fixed iOS 4.1 to run great on the iPhone 3G.
I was actually surprised by how well the iPhone 3G performed with iOS 4.1. In some tests I found it to be more reactive than the iPhone 3G was when running 3.1.3. Most people were led to believe that the Spotlight Search indexing was probably the biggest culprit. With that in mind, I navigated to the Spotlight Search settings and to my surprise, it was fully enabled. By the way, if you're running iOS 4.0 on your iPhone 3G, there was some misunderstanding as to how to get at the Spotlight Search settings. You click on Settings > General > and then the Home Button. From there you can customize what parts are being indexed.
In summary, it looks like Apple finally fixed the issues that iOS 4 was having while running on the iPhone 3G. Now the bigger, unanswered question is how did the iPhone iOS 4 / iPhone 3G version ever get shipped? It was definitely a marketing move to push this one out, given that they wanted to say it was compatible. Apparently, the people in charge didn't think that people would actually want to use it.
If you have not yet brought your iPhone 3G into the Apple Store to have it swapped for one running 3.1.3, you might as well hold off. I'm hopeful that iOS 4.1 will ship this week, moments after Apple's announcement on Wednesday. We won't know for sure until Wednesday, though. In the interim, feel relieved that Apple appears to have fixed iOS 4.1 to run beautifully on the iPhone 3G.