figure 1: the most important feature is highlighted
There's another password manager on the scene, and this one looks to be the most secure version that I've seen. 1Password is a mac-only application, so there unfortunately isn't a password manager I could securely recommend to Windows iPhone users yet. The application has a little button that sends an encrypted bookmarklet to Safari that you can then sync to your iPhone. You can open the bookmarklet and view your passwords with a master password that you assign within 1Password.
The bit that gives 1Password the nod above others at the moment is that the bookmarklet is encrypted with good cryptography. The blowfish cipher is a well-respected cipher by Bruce Schneier, one of the most respected cryptologists out there, and 1Password uses blowfish's maximum key length of 448 bits within the bookmarklet. So, if you're looking to store your passwords with heavy-duty security, 1Password might be worth your look.