Not only is the gameplay some of the best I've ever seen in a 3D platformer, but the writing, characters, story and setting are also all top-notch. Jordan Mechner, the creator of the original Prince of Persia, worked on this game and it shows. The only (minor) gripe I have is that the combat is a little dull. Everything else shines.
In the sequels to this game (which did not involve Jordan Mechner), they made combat more fun but unfortunately sacrificed the great writing and story, leaving the whole package (especially in the second game... ouch) lacking. Sands of Time stands out as the best of the trilogy by far, and at $9.99 you can't go wrong.