Superb port to the DS!
The resolution is crisp, the frame rate/fluidness of the people/rides/scrolling even when the park is packed (I remember massive slowdowns and lag when you park was very big) is absolutely brilliant which adds to the quality of the game.
The control system and screen usage is exceptionally good as well. The stylus control is accurate and easy to use; laying paths and rides is an absolute doodle (arguably easier than using a mouse was!). The screens flip seamlessly so you can always see what your park is doing even when you are in menus and works very well.
Staff/Stock negotiations are very well done as well; instead of having a plate biscuits to indicate the time remaining, the top screen now showing an hour glass with a count-down timer giving you the precise time you have left to negotiate. Also the hands move very smoothly now which allows you to tweak the negotiations in your favour easily.
My only major gripe is that you can only have a single save-game which means you can't let others play and save their game without erasing yours in the process which I think is quite a limitation.
Overall this is an excellent game for the DS and everyone should be able to get a lot of enjoyment out of this classic perfectly preserved from the past.