Yes, iCloud Keychain (even under Mavericks and iOS 7.x) syncs across all devices - if you've allowed Safari to save the password to a web site on one device, it'll be available on your other devices. One particularly nice feature is that wifi network logins are also synced among devices, so if you logged into a network with your iPhone at some point, your iPad and MacBook would automatically login to that network. Keychain can also be used to generate strong passwords.
However, not all Keychain items are available on iOS or OS X - so if, say, you create Secure Notes in the OS X Keychain - no way to view them in iOS. The stored credit card info in iOS is not accessible via OS X Keychain Access Utility. While stored wifi logins are synced, you cannot view the login password on iOS.
Three other places where Keychain falls down are when using browsers other than Safari, in the ease of access to stored data, and in the amount/type of data fields stored in each record.
the amount and type of data associated with each entry is also more limited than third-party password products. In OS X there's a single Name field, that will contain the complete URL of the web site, plus display the username in parentheses in the browser view. There's no place to enter a searchable, descriptive name for a web login, such as "My Bank." While there is a Comments field, it is not searchable. And in iOS? The Comments field is not displayed at all, and there is no search function - just scroll until you find the login.
So, while iCloud keychain has been very convenient, it's not a complete solution. I still use a separate password application as well.