Some iPod Touch users may have experienced some lag. For me, it was lag on the touch screen keyboard on the iPod Touch 8GB 3rd gen (same as second generation). They keys would have a delay before popping up. Others have mentioned very laggy YouTube videos. My iPod Touch is no jailbroken, so I looked for a solution and finally found it.
The way to fix this was to reset the iTouch (that is, completely turn it off and turn it back on). My theory was a memory issue (having several years of experience in computers and owning several other linux-based mobile devices, the problem seemed to be insufficient memory). The only thing which confused me was the fact that there is no multitasking on the iTouch. I downloaded an app to show me the processes and I was able to put it all together.
What I saw in the Process Viewer App was 15 MB of RAM being used by Safari (The internet app). I found that when safari was fully cleared, all 15MB were freed. Here is how to clear Safari and free your memory: Open up Safari. At the bottom of the screen, touch the “window” option (the very bottom right). You will be presented with all the ‘tabs’ open in safari. Tap the cross at the top left of each to close them all. Once all are closed you should get to a ‘blank’ page. Now you’re ready to push the home button at the bottom and start using your other apps again.
This successfully frees the memory (15 MB in my case) which Safari uses and makes it available to other applications. For reference, the iPod Touch has 128 MB RAM (256 MB RAM in 3rd Generation 32 and 64 GB models). Yes, it’s not convenient, but it fixes they keyboard and YouTube lag, and it’s faster than restarting the iPod.
To free even more memory, you may be interested in reading how to Force Quit Applications on the iPod Touch/iPhone to free memory.