I've herd, and felt the lack of magic that RCT3 has compared to it's older siblings, and at first i was dead set against buying it. I was bored, and bought it on amazon for $20 and it was totally worth the price. One thing you have to put aside to enjoy this game is that it's not RCT2. The scenarios are not good (too easy, too quickly completed), but that isn't where this game excels. The massive options made available from start and even a sandbox mode are amazing tools for designing new rides or even managing a huge park. The modding community also has attacked this game, with new supports and special objects for creating even more realistic parks (even custom rides). If you liked the way the old games played, this isn't for you. If you want a huge sandbox where you can build amazing or impossible rides, pools, zoos water slides, or what ever, buy this now. Ten dollars is well worth the price. I payed twenty and would have payed more. Aside from the minecraft, this is my favorite creation game.
Rollercoaster tycoon 1 was what started my never ending need to build roller coasters, but when this game came out, i freaked. There are so many options to build the park of your dreams, including advanced scenery placement (Shift to raise pieces, Ctrl to place a piece at the height as one the mouse is over), roller coaster builder, and even a park designer. The third party development is amazing as well. You can go to so many different websites and download custom content. Google USES, or User Created Expansion Pack RCT2.