If you have your iPod Touch or iPhone backed up via iTunes, it's very difficult to "brick" either one. Recovering from any mis-steps is not hard and easily found on the Net if one Googles.
I jailbroke my iPod Touch (again) on iOS4 using the www.jailbreakme.com web-based jailbreak.
All I got with iOS4 was folders. No UI customising. No multi-tasking. I had both with my jail-broken v3.1.2 install prior to allowing the upgrade to iOS4. Big disappointment.
But I'm jailbroken again and much hapier for it. I can now multi-task again (Backgrounder)...and my iPod Touch screen is much better looking now (Winterboard)...and the icons are much smaller (Shrink).
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