I've never used it on one of my sites but I don't like it on other peoples sites. I don't like how it changes sites. The login, different urls, time outs, etc. It's annoying and can cause conflict. Plus the image verification doesn't work on a lot of sites. It will give a word like "flip" and you can type in "flop" and it still lets you in. I prefer to use, and have used for many years, Password Sentry.
http://www.monster-submit.com/sentry/