What is the best way to check the performance? When I started out it was about the money. Then it was about links and traffic. Neither is that important to me right now - and for the past several years - it is about SERPS.
I usually go to analytics and see what pages are getting the traffic. I check the keywords and then look it up in Google. Then I print that page and check it a week or month later. I'll print up a bunch of pages and just check them from time to time.
If you don't do something like this, there is no real way to tell how Panda affected you, right? Clicks don't tell you. Traffic doesn't tell you. $$$$ doesn't tell you. All of those seem to be the result of the SERPS, right?
What is your method of measuring how well your site is doing?