AppleInsider has links to Apple Discussions of 3rd party app crashes or hangs. Other reports of lags in the interface operations and audio echoing. Unreliable GPS mapping and non-working tilt sensor reported by a few users.
iPhone 3G Lag is intolerable! Video examples included.
None of these issues affect the original iPhone even running 2.0.
Also reported is that Apple is working on a 2.0.1 update.