I just upgraded my iPad to 4.2.1 and jailbroke via redsnow. I must say that despite the fact the jailbreak is tethered, it's very stable. I don't restart my ipad that often so it's not a huge issue for me. Cydia works great and slowly but surely everything is being updated. The new os is great. My only issue is with multitasking, its stupid that there is no way to choose which apps you want to multitask, instead of multitasking everything and clogging up the tray. When the new untethered jailbreak comes out I will surely upgrade to it, but for now this is working great for me. I must say though, i wont be doing it on my iPhone 4 until the untethered jailbreak is out.