Jose Cuervo began bottling tequila in 1906, instead of selling it in barrels, increasing the popularity yet more. The real boost to American popularity was Prohibition-it was a simple thing to smuggle the drink across the Mexican border, and much better than bathtub gin. Belief that tequila contained mescaline made it ridiculously popular amongst the beatnik set of the same period. As with many things, it depends on your individual taste. Blanco tequila isn't aged, and is clear.
Silver is the more refined version, but is also unaged and clear.
The agave flavor is quite strong, and is very popular with tequila-aficianados in Mexico. Reposado is aged from 2 months to a year, and is a bit more yellow in color, and more rounded in flavor due to the aging. Anejo is aged for about 6 years in little barrels, quite yellow in color, and quite expensive as well. It's so well-rounded that it hardly tastes like tequila anymore. They want you to think that it's anejo, but it's just cheap-quality blanco with some caramel coloring.