Not as bad as others say
Those of you who are extreme fans of the standard Pokémon formula, leave now. This game does not concern trainers whatsoever. Instead, you take the role of a 'ranger'. This group of people don't permanently capture pokémon. Instead, they calm them down using their 'capture styler' (i.e. your stylus) and get them to help you out of their own free will (supposedly).
Basically, you perform missions by finding pokémon, draw rings round them repeatedly and then let go to catch them. 'Simple' is not the word for it though. Pokemon attack your rings and generally make it difficult to get them to calm down. Therefore, you use the other pokemon you catch (and extremely fast circling) to help you in all matter of ways.
Overall, the gameplay is rather repetitive, but fun (and that's what games need to be: fun). The difficulty curve is reasonable with pokémon getting smarter as you go along.
Those who haven't seen the point yet, you start by doing missions for the people in the nearby towns and helping them with their pokémon. Later, however, you'll be dealing with pokémon who have been forcibly captured by evil (but comedic) people. No pokéballs here by the way. They all use stylers like the rangers use. Therefore, the pokémon will leave when they calm down.
In all, it's a rather good game, but it can get repetitive. When you get fed up, leave it for a few hours and you'll be drawn back for more.