As with any advertising, you have to take teeth whitening hype with a grain of salt, or aluminum oxide or calcium carbonate, as abrasive ingredients go, which all toothpastes have to some extent. A few also boast about containing a "bleach" type ingredient, typically hydrogen peroxide, but studies have shown that these really have a negligible whitening effect.
The answer to question of, "Do teeth whitening toothpastes really work?" is yeah...kinda, it depends. Seriously, though, they work only to the extent that your discoloration is strictly on the surface. The mild abrasives combined with the scrubbing motion of your brush, will remove topical stains from coffee, tea, wine, nicotine, etc. However, swishing your mouth with water after finishing your morning coffee and brushing and flossing daily would also reduce/prevent those stains.
Teeth whitening toothpaste won't lighten the natural color, or correct any discoloration due to damage. The inner part of the tooth, dentin, naturally yellows with age (as well as certain medications and excessive fluoride use), and teeth whitening toothpastes won't do a darn thing for that. The better bet would be to talk to your dentist and get a professional bleaching done. Afterward, it may be beneficial to use the whitening toothpaste to maintain your magazine cover gleam.
Speaking of a GQ gleam, whitening toothpastes that contain blue covarine have been shown in studies to immediately give the appearance of whiter, "gleamier" teeth with one use. Being blue, it cancels out the yellow and adheres to the surface to create the optical illusion of super-white teeth.