I just finished this game about a minute ago. And my goodness was it fantastic! Gameplay is greatly improved. The main aspect that was improved is the capture method. Although pretty much the same as the old game, to capture a pokemon you don't have to continuely loop it, you can take a break from looping. The 'friendship feelings' will stay with the pokemon for a while, allowing you a short break while the pokemon attacks. This meant that really, poke assists were a bit useless, but that was fine by me.
The addition of being able to swim under water, ride on floatzel, mantine, empoleon, torkoal etc was also pretty cool. I mean, there is nothing more awesome the surfing on lava!
You can catch Staraptor and fly on them, or ride doduo to get around a bit faster. There is a better variety of pokemon this time too. The only problem was the lack of save points. Luckily my styler only broke twice in the game, but at certain points, I could imagine how awful it would be for it to break, when you hadn't been to a save point in over 30 minutes.
Get this game before the end of February '09 to download the special missions from Ranger Net!
I couldn't put this game down, my poor DS is worn out. I think it deserves a rest now, but only once I have completed the extra missions!
If you are a pokemon fan or not, get this game.
An additional note, don't get put off by the first hour or two of this game. It was very slow to begin with, but persevere, because it just keeps getting better!