Yeah it's a nice change -- especially for new users. Personally I don't want to upgrade my JB'd 3GS on 3.2.1 to a non JB'd 4.0.1 then re-JB. I'm just going to use the custom IPSW from the dev team
why? It'll be the exact same thing. Either way you will wipe your phone to install the update.
Plus there's no guarentee the dev team will release a pwnage tool since ultrasn0w works on all basebands (and they did help comex with this jailbreak).
I'd just update and do the jailbreak.
It feels great to be jailbroken again.
I can't wait for someone to jailbreak every device in an apple store since it's done from the phone. HA!