I like last pass, I trust it fairly well. The important rules are:

• Use a STRONG master password.
• Turn on the "Require password reprompt" feature for important/valuable sites.
• Set the auto log off when idle feature.

A nice thing about last pass is that your passwords don't actually make it to their servers - your vault get decrypted on the client side and only with the master password. I like using a unique 32 character password (letters, numbers and special characters) for every site I use.

The only danger is if you get a keylogger, but I'm not too worried about that since I keep my computers secure (hardened linux everywhere - not invulnerable I know).