I believe the correct question is: when is the best time to buy what market segment?
I think different companies and different sectors will bounce back quicker, or lag behind longer. An index tracker will smooth that out for you, but will also "dull" the benefits of the upswing. Picking the right stocks, the right industries, AND the right timing will be a real challenge in this market we're now pioneering. It's not for the faint of heart.