Right now certain models ofiPhones, iPod touches, and iPads running iOS 4.2.1 can only be Jailbroken via the "tethered" method which means they need to be plugged into your Windows or Mac PC and rebooted via a program, redsn0w. Not just to Jailbreak them, mind you, but anytime you need to reboot your iPhone, iPod touch, or iPad. Forget whether you should Jailbreak or not, tethered Jailbreaks require so many extra steps, do the benefits still make up for the hassle?
Finish jailbreaking. Reboot. Update Cydia. Reboot. Update Cydia again. Reboot. Install a Jailbreak app or tweak. Reboot. Install another. Reboot. Hang or crash. Reboot. Run out of power. Reboot.
And it's not just a simple reboot, you have to run redsn0w, power off your iPhone, iPod touch, or iPad, find your firmware on your PC, load the firmware into redsn0w, let it process, make sure you uncheck Jailbreak and check Untethered boot, put your device into DFU mode, then let redsn0w work its tethered reboot magic.
As Jailbreak Forum members will attest, real hax0rs don't mind tethered Jailbreaks, but compared to an untethered Jailbreak it's a pain in the @$$, especially when you have a lot of new, or updated stuff you want to install. But then you get to use things like AirVideoEnabler which lets any AirPlay app send video to Apple TV, among a lot of other very useful apps. And you get to Jailbreak an iPad running iOS 4.2, the first iOS 4 version available for iPad, which is a tremendous upgrade in its own right.
Sure Comex and his miraculous userland exploits will probably make 4.2 an untethered Jailbreak before the end of the year, but iOS 4.2.2 or iOS 4.3 or iOS 5 will eventually come around and, if we want the latest firmware, we might be back to tethered for a while. Is it worth it?