[mikeash]

While jailbreak hacks are really cool, you can't really base any long-term decisions (like hardware purchases) around them, because jailbreaks are so unpredictable. It's a crapshoot as to whether any given OS version will have a jailbreak, and who knows how long it will take. Even if you wait for the jailbreak to be released, there's no real guarantee you can keep it. The next OS release will probably break it, and even if you refrain from upgrading, it's likely that you'll eventually be forced to upgrade due to a hardware failure, OS corruption, inadvertent button press, massive widespread security hole, etc. And good ol' Apple doesn't let you install older OSes after new versions come out, even on hardware that supports them.