We've already pointed to disabling Spotlight and hard resetsas ways of improving the sometimes sluggish performance of iOS4 on older iPhones. Lifehacker reader Daniel has another suggestion: get rid of excess text messages.
Picture by rockbandit
I am part of the crowd that still has an iPhone 3G with iOS4 loaded onto it. I have, like everyone else noticed significant performance decrease since the update. I have tried many fixes, but the one I have found that helps the most is deleting text message conversations. I am not sure why, but it definitely has helped keep me sane while I wait for the iPhone 4 upgrade.
While not everyone who has upgraded has experienced performance issues, they certainly seem common enough -- and varied enough -- to make any potential improvement worth trying. If the whole experience becomes too painful, check our full guide to downgrading from iOS4 back to 3.1.3. Thanks Daniel!