Slow boot OS Lion on Macbook Pro
You could press &#x2318;+v (verbose boot) at startup. No Apple logo will appear, but the screen will turn black and print a lot of text as it boots up. (As soon as the OS has booted, it will go into graphics mode, don't worry.)

Whenever an action takes very long and it prints some message (either in progress or afterwards), write it down or take a photo of the screen. You can then google for this problem.