If you didn't already know, limera1n is untethered only because of a userland exploit developed by comex. If you are on 4.1 and a new firmware has been released, the devs can release a tool that will update your iPod, while removing the userland patch in the new firmware. This means that you will be untethered forever. Although we will all be able to do it once, since every firmware is vulnerable, you will have to downgrade to 4.1 first to do this in the future when you are already on, say 4.2. So this means that you need to backup your SHSH blobs for 4.1 using TinyUmbrella ASAP! You can use Extra A in the jailbreaking guide in my sig if you need instructions!