In the morning I presented a video which, although it was categorized as a parody, still presents quite well the situation of iPhone 3G owners who have iOS 4.0 installed. If, however, your system does not move so badly and you want to benefit from multitasking or the possibility to set a wallpaper in the background, then zToggle is the perfect application for you. zToggle is a small tweak from Cydia through which you can activate/deactivate, with a simple button press and a respring, multitasking and the option to set wallpapers. I know there is a similar tweak, it's called Features, but unlike zToggle, it only works with Winterboard.
zToggle only works on iPhone 3G, so don't try to install it on other terminals, and it is available for free from Cydia through the BigBoss repo.
