For us jailbroken folk, Lance has updated the Backgrounder app to run in iOS 4.1. This is good news for iPhone 3G users who have little free ram to play with, as it means you can (among other things) set which apps you want to background and which ones you want to quit properly when you quit them. Of course, the main thing Backgrounder offers is the opportunity for real backgrounding of apps, i.e. instead of iOS4's 'freeze when in background, unfreeze again when brought forward' version of backgrounding, this app lets apps run properly in the background, providing real multitasking. Of course, your battery will bow its head faster this way with apps that are using more resources, but it's worth it to have things run properly in the background, and to lose the lag switching apps on a 3G.
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If it's brokenless, don't suffix it...