The new Apple iPhone OS 3.0 has had over 6 million downloads since its release with the new firmware working not only with the new 3G iPhone but also with the original.
We have found via Gearlog that the new firmware is causing the battery life on the older versions to nosedive also causing the phone to run hot. There have been a few reports of battery life drop which primarily attributed to debugging software but I am sure you would agree as this is a final release you would not expect this to happen.
The newer-hardware is apparently unaffected and Apple need to resolve this problem very soon as this is not an isolated problem (hopefully it will be resolved very soon).