Really well executed extension. This thing stays out of the way but lets me know how things are going. On browser restart if you have 70 to 700 tabs it takes a while to catch up and there is some update lag when you delete tabs to clean up but that is most likely not a problem with this extension (more like a problem of having too many tabs open :-)).
I have a list of 7 extensions I always install and this is number 3!