The Vault pseudo-app's menus are almost empty, and there's no way to customize the way in which entries are shown. Choosing Undo after creating a new entry crashed the app. Buttons in the Vault and other dialog boxes are odd — like they belong on another platform, but which one? I'm not sure.
The browser plug-ins are better designed and seem more mature, although they also have a very technical field and are rather chatty. When logging into a site, the plug-in alerts you about using a stored login, and also displays an overlaid box on the page that says a page is loading, and then that it's loaded and the login data has been submitted.
Applicable form fields have the LastPass asterisk icon in them, which you can click to bring up matching entries or perform other tasks. After manually entering or using a browser-stored account login, LastPass shows a subtle but persistent bar along the page's top offering to store the login, as well as temporarily or permanently ignore it.
A little more polish, please
In testing, the app seemed unfortunately unstable. Fine for long periods, it would sometimes cycle through logins, logging itself out and then, when logged back in, launching the vault window and pushing it foremost in OS X. This seemed to affect syncing as well. There are polish problems all over: form fill is sometimes called FormFill, sometimes Form Fill, and sometimes (lowercase) form fill.
The app has the surface feeling of ported software, instead of a native OS X program. This starts with the menu options. After installing, you can launch it, which opens the Vault window, but closing the window removes the app's icon from the Dock. A menu bar item is persistent, from which you can select Vault. Choosing Preferences from the menu or from the Preferences item that appears, and then clicking Cancel bafflingly closes the Vault.
From a security standpoint, after an interval you specify has passed during which the vault remains unlocked, a master password request appears. However, it comes up without blanking the vault main display, allowing account names and other information to be viewed, unlike 1Password, which secures the display when the timeout occurs.
LastPass for OS X isn't ready for general use without additional polish, user-interface design, and debugging. It does store and fill in site logins as promised, but unless you need its web-based access or already use LastPass via plug-ins or mobile apps, I cannot recommend its use yet.
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