Review: iPhone 3G
Screen
The new screen is similar to the first in that it bright, has high resolution, and is very readable in bright daylight. The new one has been tweaked with software to make things appear more "natural". In reality, this means it looks "yellower" than the original iPhone's screen when held in side-by-side comparisons. First-time owners won't notice this. This can be corrected, however, if you sync your store-bought 3G iPhone, and use iTunes to "restore" the 3G iPhone. Restoring the 3G iPhone will install a slightly updated version of the 2.0 firmware, and correct the yellow tinge.
Signal
Before buying the 3G iPhone, I mapped out the signal strength of the original iPhone in all of my usual test spots for AT&T signals. The 3G iPhone performed pretty much on par with the original when it came to EDGE (2G) reception. No better, no worse. This means it does an okay job. The iPhone is not a signal hound. Compared to a Nokia N95, which was accessing AT&T's 3G signals, it was typically a bit weaker than the N95.
Sound
There's no doubt, the 3G iPhone sounds better than the original. Calls are clearer, less noise, less echo, and less garbling. To my ears, the improvement was night and day. The earpiece is also louder. This helps a lot, because the original's speaker was certainly not packing a Marshall full stack in there. The same can be said for calls taken with a Bluetooth headset. They were cleaner, and suffered from less interference. Music playback did not sound appreciably different. Ringers can be made loud enough for most in-home environments, but it is still lacking compared to others when it comes to outdoor environments.
Battery
With the 3G radio active, you can almost watch the battery level indicator drop while you stare at it. With a full charge at 7PM on the 11th, I left my phone on overnight with the 3G radio active. By morning, the charge was 40% gone. I switched the 3G radio off around Noon on the 12th, and didn't reach the 20% left warning until 9PM of the 13th. I sent a hella lot of text messages, spent time browsing the web, and took several phone calls that lasted more than 10 minutes. I'd call that minimal use. Other reviewers who spent more time with the 3G iPhone noted that it typically lost a full charge in a day with the 3G radio active.