Do you have a jailbroken iPhone? You might want to check out QTweeter. Efiko has chosen not to go through the app store and deal with the restrictions it offers on the type of apps Apple will approve. I haven't tested it (I'm not Jailbroken) but it looks awesome & elegant.
It provides a very Mac like interface for updating your twitter or Facebook status. You can even make videos and music, safari, and YouTube tweets. Pretty cool stuff. Makes me want to jailbreak. It's available from the Cydia app store.
Check out this demo video.