Sadly, I think Hello on the L950 suffers from very bad implementation. When I have it turned off (just a PIN to unlock), I unlock my phone and if I pick it up at any time during the timeout all I have to do is slide the screen up to get in - I don't have to re-enter the PIN.
With Hello, every time I turn the phone on, it looks for me.
For example let's say I have Hello turned off, only the PIN for security and the phone set to remain unlocked for 5 minutes.
I unlock the phone with my PIN, do some stuff and turn it off. If I come back 3 minutes later and turn it on, it doesn't ask for the PIN again (because it's less than 5 minutes), I just have to slide the screen up to get in.
Now let's say all the same except Hello is turned on.
I unlock the phone with my eye, do some stuff and turn it off. If I come back 3 minutes later and turn it on, it starts looking for my eye again. Yes, I can just slide the screen up and get in but it shouldn't even pretend to require authentication again. When it does, it confuses me if I'm not thinking and uses battery to fire up the infrared camera and red light.
More infuriating is that some events that "wake up" the phone (e.g. receiving an email\text or other notifications) seem to turn Hello on and even though I may not even be in the room and certainly haven't interacted with my phone in any way, it's sitting there looking for me.
Bottom line is that when I have Hello on, my battery drains in half the time due to all the time Hello is looking for me when it shouldn't be. Hello should work exactly the same as just using a PIN but allow one more option for authenticating.