When Google introduced Smart Lock to Android it seemed like a piece of genius: use information about a device's location to decide whether the lock screen should be enabled. Despite the fact that it works well, I've stopped using it and I suspect that most users with Android phones with fingerprint sensors will want to do the same.
On the Galaxy S6 I have got into the habit of waking the phone by pressing the home key. By keeping my finger on the key a little longer than normal it gives the phone a chance to read my fingerprint and unlock the device. Its such a natural process that I do it without even thinking about it.
Which means trouble when smart lock activates, because Smart Lock disables the fingerprint login and enables the swipe lock screen.
So when Smart Lock is activated I find that I'm left looking at the lock screen wondering what's going on because I'm still trying to unlock with my fingerprint.
For users who don't have the option to use their fingerprint to login Smart Lock is a brilliant tool. For the rest of us it needs some more thought before it's useful.