I've used Credit Karma for a while now. One thing to note, Credit Karma doesn't use the FICO model which is far and away the most popular credit scoring model and the one most lenders (over 90%) use. Credit Karma uses VantageScore 3.0. I use it mostly as a monitoring service. Credit Karma is actually really quick about notifying you of new accounts opened in your name or when you have a hard inquiry...often in the same day. It's a pretty handy tool. Most credit cards offer the same service now.