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here is a idea

wait till 3.1 official release comes out, then after sometime hopefully a JB will come out for it then it's worth asking. the DEV team nor anybody else makes JB for beta's ;)
 
I'm so happy with the JB apps I currently have installed and how well my iPhone 3gs is running that I'm in no hurry for a 3.1 jailbreak.
 
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