2 years later and still not too bad
Pokemon Diamond and Pearl has sold millions of copies worldwide, which means if you're thinking about buying this, you probably have a Nintendo DS and Pokemon Diamond or Pearl for it. If this is your case, then purchasing this is probably something you should think over. But if you are new to the series or you don't own Pokemon Diamond and Pearl, then Pokemon Platinum is probably the best game to start with.
Despite it [Pokemon Platinum] being new to the series, there are still many similarities to it and it's predosseser, enough to leave me pondering if getting this was a real good idea. But there's a pretty good balance between those similarities and the new features, including a few new characters including a person/crackhead named Looker, advanced Wi-Fi options including the Wi-FI Plaza and the sharing of stats, as well as improved visuals. Many tiny plausible issues have also been fixed; now you can move up and down on the watch! The strategy has also changed too. The order of gyms has changed and the ownership has also been changed. For example, if you battled a Pikachu against Bob in the previous games, now you'll probably battle against Bob's new Pichu, not to say that every trainer now has weaker Pokemon.
The new Wi-Fi features aren't too bad. The two biggest are probably the additions of the Wi-Fi Plaza and the battle recording. In the Wi-Fi Plaza, which can be accessed at any Pokemon Center, you can play minigames with other people, talk to other people, and play or trade toys you get when you enter the Plaza. Granite, the plaza isn't truly impressive, but it's a nice addition. The other biggest addition is the ability to record your battles. You can save your own battle videos of playing against other people and upload them for other people to view, and you can also download other people's battle videos and view them. Unfortunately, you can't save videos of playing people in the game, such as against the Gym Leaders or people at the Pokemon League. But it's a brilliant idea.
Other than that, there really isn't much more than quotes from the Pokemon Diamond/Pearl reviews. Pokemon Platinum, at it's core, is just an expansion to Pokemon Diamond and Pearl including some handy and fun new features. But even 2 years later, it's the addictive RPG it's been for more than 10 years.