Hello, I've recently upgraded my iPod Touch 2G to iOS4, and it feels much slower to me. I've seen people complaining about that in other threads (iPhone 3G too). One idea that I had while playing around with the OS is that maybe the new multitasking feature is making it slow. From what I understand, iOS4 saves the memory image of any previously launched applications in the background. My understanding was that it saves the image to disk. However, some experimenting makes me think that the image stays in the memory. Which as a result makes less memory available to other apps. I only did a quick test to check this hypothesis, so I might as well be wrong. I'll be doing more "scientific" tests this evening. But in the meantime, let me know what you think. So far, this is what I did. I launched a random application, closed it by clicking the home button, launched another application, closed it by clicking the home button.... you get the idea. Then from the home screen, I checked the amount of available memory using SBSettings (I have a jailbroken iOS4). After launching 11 apps (Facebook, Twitter, Safari, Mail, cardmath24, Cydia, iTunes, AC-130, App Store, iBooks) I have 10MB of memory available. Then I kill all of the apps. I do this by double clicking the home button, so the app switched pops up, holding down an icon in the app switcher so it goes into edit mode and pressing the red "stop" button in the corner of each app. As a result, I have 43 MB of available memory and the OS seems a bit more responsive. But the responsiveness might just be a placebo effect. I plan to do a real test this evening. I plan to write a simple app that calculates the first few prime numbers using a brute force algorithm. Then I want to see how long it takes to do this if I have launched a lot of apps in the background and if I have not. What do you guys think? Is there an already existing app that is designed to measure the performance of iOS?