Got an original iPhone like me? Wondering if 3.0 is worth the upgrade? Worry not - I upgraded mine on day one of 3.0 availability, and it's working just fine, if not better than before. Battery life is the same, performance is snappy. How is it that Apple can continue to support, and even improve the user experience of, legacy equipment while nearly all other hardware/software vendors do just the opposite? It's remarkable. And Mrs Pinwheel's 3G is also upgraded to rave reviews.
Search, landscape keyboard, Find my iPhone (cool!), and the long-awaited cut/copy/paste are all there, and work with Apple's signature it-just-works awesomeness.
Apple has a handy chart that shows what each generation of iPhone offers what features with 3.0 here (hat tip ars technica).