Rated 4 out of 5 stars
The best cross-platform, cross-browser, independently-accessible-from-internet-cafes password manager that I've ever found.
To be honest - it's a bit difficult to review this as an add-on. It's more of a service offered in the cloud, and the "add-on" is merely a means of accessing that service. It's possible to access the service without using the add-on too, through any browswer.
My only qualm with it, is that it occasionally corrupts a few entries in my "vault" (as LastPass refer to it), at a frequency of one website every couple of months or so. This means that I have to maintain my keepass file in synch with LastPass just for backup purposes, which is a bit of a maintenance overhead.
Still, it's well worth using, because the time it saves in logging into websites when it does work, far outweighs the few minutes of maintenance required for managing the backups.
Edit: For those who have mentioned that you like to store your passwords locally, and don't trust the cloud for managing them, I can only assume that you don't use your password manager in the way they've been designed to work! KeePass (and others) are great in what they are, but you need to have the application installed to access them (which I don't at the office and at my friend's house), and you also need to keep the encrypted file synchronized between PCs. Some might reply that they can memorize their passwords, so they don't need to access passwords at the office. But that only begs the question of why you are using password managers at all?
@Matt Sayler: In case you haven't noticed, this is a web-browser addon you're reviewing. Seems unfair to mark it down on account of you wanting a desktop-app!