What can I say, this is a great addon ever developed till now. It helps lots of webmaster in cut down the time to make research on every site they've visited. If you think SEO is a part that must have in getting a success story in internet marketing industry, then SeoQuake is a must addon you should have!
I like it. I compared it to the google toolbar and found that it gave the exact same rating 99% of the time. (only found zbikers.ru website that it gave a different rating on but it wasn't a big deal). I prefer this add on to google toolbar as it doesn't clutter up my toolbar as much. I don't use any of the other buttons however, and there are more accurate ways to get backlink numbers then with this add on. But worth it for the page rank alone. Agree with above user that if it simply gave a number for a page rank then showing a green line...it would be even better.