This was the easiest update I've applied to date and it has improved the overall responsiveness of my (original) iPhone -- rather significantly. However, when you perform the upgrade, use a USB port on your computer not a port on an attached hub and not a third party internal USB card port. Otherwise the upgrade is likely to stall, and you will have to restore the iPhone to its original settings before upgrading.

Also, unplug any USB devices not required during the update process. From that point on (after the firmware update is applied successfully) you may reattach all USB devices and revert back to using a USB hub or third party internal USB card port for day-to-day use.