Apple has released iOS 5.1 and stopped signing for older version of iOS 5.0.1. That means that if you buy a new device (such as the new iPad) that comes with iOS 5.1 by default, you are left with tethered jailbreak unless you downgrade to iOS 5.0.1 which already have untethered version.
Well, the good news is that it's possible for us to downgrade to iOS 5.0.1 even after you have upgraded to iOS 5.1. Unfortunately, there are still no public releases on tools used to perform the downgrade, so we need to wait for few days/weeks before a public release is coming out and users will be able to downgrade their A5-based devices. See FreakGeeks for more information about this news.