State of Javascript client side error tracking

I made a rant about javascript error logging state of the art :

1. Interesting Hacker News discussions -
a) Rescue.js : Not in production now, but thread is interesting to read -
b) How to do it with google analytics:

2. Products and methodology -
a) Sentry : Looks very promising but not free :,
b) A YC startup around it : Proxino ( Yeah ssl certificate is expired, looks like guys are not in action )
c) An another MVP around the idea : ( looks like dead to me )
d) Old school way :, ( Warning try, catch ahead )
e) Clicktale :

3. Looks Promising -
a) Airbrake : Looks promising ! Read here about their state of the art :
b) Exceptional :
c) And of course Errorception: