All of your non jailbroken stuff is saved in Itunes after you sync and backup. Contacts,Media, Ringtones, Movies, etc etc. Your non jailbroken stuff will have to be redownloaded when the ios5 jailbreak comes out and you go that route. But theres a few jailbroken apps that make that part easier for you. Jailbroken apps that you payed for can also be retrieved without having to pay again. You will sign into Cydia with your Amazon or Google Log In.
In simplest terms when you upgrade software you lose your jailbreak and jailbreak apps everything else is on Itunes when you upgrade contacts, etc will all be back on phone.
Josh
A good useful trick I do. Is go to your Cydia packages and take a screen shot of all your Cydia apps. Than when everything is finished upgraded to Ios5 and jailbroken you can go to your pictures and see what you had downloaded.
Hope this all helps.
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