EDIT: YOU CAN NOW RUN THE 2.0 FIRMWARE ON A 2.5G iPHONE BY USING PWNAGE 2.0. To download it at check here for links (this is tool does require some basic knowledge, most should be just fine) http://blog.iphone-dev.org
I can confirm the 2.0 firmware works perfectly,
2.5G iPhone running the 2.0 software, using PwnageTool 2.0.1 on vofa NZ prepay.
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I've just spent an hour getting it back to 1.1.4
But I can tell you the upgrade takes a long time, the IPSW is 200mb+
If you upgrade to 2.0, iTunes tells you to activate with AT&T and there's no jailbreak or activation bypass yet.
If you need to get back to 1.1.4 intructions are here
Hopefully a jailbreak will come out soon!


