3GS is an excellent phone and should continue to sell, post ip5.
I agree with the recent comments on the way ip4 feels in the hands compared to the curved shape of yesterphone. I previously owned an ip3G and chose to go with HTC's desire due to both price of the ip4 and also the rigid shape / feel.
Going back to comments previously on the iPhone being free in the UK and eurozone countries, it works out around the same.
At current exchange rates:
UK
iPhone 4 White 16Gb - 1Gb of Data / ~1000Mins / ~5000 Texts
$0 Up Front / $72.30 per month (This is £0.00 Up front & £45.00/month)
24 Month contract
US
iPhone 4 White 16Gb - Unlimited Data / ~450 Mins / ~5000 Texts
$199 Up Front / $89.98 / $35.00 Activation Fee
24 Month Contract
So to conclude...
UK - Total Cost of Ownership
£1080 ($1735)
US - Total Cost of Ownership
£1489 ($2393)
If my maths serves me well thats a £409 / $658 increase just for living in the US. Frankly even if you did get everything first, it's still not worth it.
Please dis-regard my last stated comment "it works out around the same."
I will however say thanks to the innovation in technology that the U.S has punted out over the last few years, even if it was all possible thanks to my fellow scot, Alex G Bell.
Have a nice day
