First thoughts on iPhone 3G:

• I prefer the metal back on the original iPhone. I do understand, though, that it has a negative impact on radio performance and hence battery life.
• The metal buttons on the iPhone 3G don’t appear to be very well finished. I’d have rounded the edges off a bit more; they seem too sharp to me.
• The silent mode switch is significantly stiffer on the 3G. I think I prefer the original feel, but I understand that some people kept knocking it, so maybe the change is necessary.
• The iPhone 3G is physically slightly larger, and the display has a slightly larger border as a result.
• The colour temperature of the display has indeed been adjusted. This is a Good Thing, as I always thought the original iPhone was too blue.
• The touch screen on the 3G seems slightly more responsive.
• iPhone 3G seems like it might be a little quicker than the original. This is just subjective, I haven’t measured or looked at the devices in it, so it may well be entirely imaginary.

Of course, the GPS and 3G features will be useful, particularly in the part of the U.K. where I live because EDGE coverage is patchy so with my original iPhone I ended up having to rely on GPRS which is pretty slow by comparison to EDGE, never mind 3G data. 3G, on the other hand, has pretty wide coverage here in the U.K.