Jailbreaking Ipod Touch...?

Should I jailbreak my ipod touch, I dont have an apple warrenty. Are there any drawbacks to jailbreaking it, what is good about kailbreaking it. What are some examples of what you get when you "break" it. Also, if I jailbreak it do I still have to pay for the january update? Say, I get the update after jailbreaking it, if I decide to get rid of the jailbreaking...how do I do it, and will everything I've gotton with it disappear