I haven't had a regular checkup since college. Probably should. Although I recently read that the theory on this is changing. Some recent studies (generic enough for ya?) have suggested that for most folks, getting regular medical advice when you go to the doctor for other ailments is as effective in detecting and preventing illness as scheduling annual checkups.
Myself, I've had various procedures done when I've been to the doc for specific complaints that give me indication that things are in pretty good shape.
For example, my blood pressure, blood sugar, etc. are fine. I've had skin cancer screenings and have no real chronic issues...so...
Still, I should probably go.