Apple just released 4.3.4, which patches the Jailbreakme PDF jailbreak.
So, iPad 2 owners, DO NOT UPGRADE!!!!!!!!!!!
iPad 1 owners, you can upgrade, as longs your SHSH blobs for 4.3.3 are saved. But there is no jailbreak for 4.3.4 yet so upgrading is pointless.
F4780y gives more info for iPad 2 owners.
According to a member, the 4.3.3 window hasn't closed yet.