Unity is a multiplatform game development tool, designed from the start to ease creation. A fully integrated professional application, Unity just happens to contain the most powerful engine this side of a million dollars.
Unity was the best development software I have ever used. Hands down. The company I work for has been using it for the last 4 years and it's been a pleasure. We just finished our latest game, Tropical Heat, a jet ski racing game that takes place in the tropics, which we developed for PC, Mac and iOS using Unity 3.5. We look forward to upgrading to the latest version when we start our next game!
You are given anything you need to create the gameplay for your game. Both 2D and 3D. Most features in the Pro version are for creating better visuals. It is possible to do advanced graphical features without Pro version, but then again, the performance might not be as good as Pro counterpart.