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I'd wait, new iPhone will probably be more desirable than new one and you'll be disappointed every time you look at your obsolete 3G iPhone. Having said that I loved my current and original iPhone, and you might be happy with the 3G iphone. I'd still wait though.

To some of the other repliers- why bother to give the OP a hard time for asking a question that he'd like help with? If you find these threads boring / irritating / annoying etc. ignore them. Post on a thread worthy of your attention and time.
 
The iPhone is pretty cheap since you get the App Store, something that no other smartphone has. And Sony's XPERIA junk is $800... I'd say wait for the next one (3 months at most).
 
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