It's true, there's this new SHSH ID associated with iOS4 and iPhone 4 but when you jailbreak and run cydia for the first time it backs up original ID so it can fool itunes.
Basically it will use the hacked ID when you're accessing cydia and regular ID when you're accessing iTunes store. It's pretty simple, really.
Check out the first video I made with my camera at
http://www.torontocarforums.com/toro...-new-post.html it's pretty decent quality. Of course the YouTube version is YouTube quality.