Three weeks after the release, Apple updates iPhone Software 2.0 to address numbers of issues.
Details are a little bit sketchy at this moment, but it is expected for Apple to address the stability and performance issue regarding the iPhone Software.
The update is available through iTunes with iPhone/iPod touch plugged-in.
Another note of interest, that there are two different iPhone Software 2.0.1 for the iPhone and iPhone 3G.
iPhone Software 2.0.1 for iPhone 3G is labeled iPhone1,2_2.0.1_5B108_Restore.ipsw and weighs in at 249.1MB.
iPhone Software 2.0.1 for iPhone is labeled iPhone1,1_2.0.1_5B108_Restore.ipsw and weighs in at 242.3MB.
Anecdotally, the iPhone 3G running Software 2.0.1 feels a zippier.