If you want a game with great features, old-school music, and good taste, take a look at this game!
Pro: The original battle system from Pokemons Red and Blue, giving it a nostalgic feel.
Con: Repetitive music, making going through areas sometimes boring, and REALLY annoying.
Pro: Lots o' new Pokemon for you to catch and train. If you could count the varieties, you wouldn't be able to.
Con: While the music is like Red and Blue's, old-school isn't always the way to go.
Pro: You may not notice it at first, but most Pokemon have different looks with the two genders. Some are quite noticeable, but some you'll have to look for with a Pokedex tool, which you get as you progress through the game.
And finally, one more con (:-( ): THE ELITE FOUR IS WAY TOO HARD, unless you level your Pokemon up to AT LEAST level 75+.
Well, I hope you enjoyed my opinions on Pokemon Diamond and Pearl. Now, one more opinion. If you're set on buying this game, then do so. This game is great. But, you may rent it if you are still skeptical. But just play it!