I use IMDb regularly, so when I saw that the app had been released, I downloaded it immediately. Upon launching, the app will ask if you wish to let it use your location -- this is used to display show times and movies for local theaters. While IMDb doesn't exactly have a beautiful interface, it's perfect for navigating the huge amount of information that is available.
The first page of the app displays three major areas: Movies, TV, and People. There's also an Application area, which is used only to display information about the App. Movies is subdivided into Showtimes, Coming Soon, US Box Office Results, MOVIEmeter, and the Top 250 Movies. Tapping Coming Soon brings up details about upcoming movies releases, including trailers that can be viewed on the phone. I love the Top 250 Movies, which is a list of the movies rated highest by IMDb readers. It's a treasure trove of information about many of the classic movies of all time.
IMDb's TV section is split into US TV Tonight, which is a schedule of upcoming shows on the major networks, and US TV Recaps, which provides full text synopses of what has happened on top TV shows during the previous week. Under the People heading, there's both STARmeter, which shows a listing of the top 25 stars as measured by the number of times that they've been searched for on IMDb, and Born Today, which lists actors (living and dead) who were born on the current day.
If you love movies and TV, or searching trivia about roles, actors, and directors, then you probably already spend a lot of time with IMDb. The iPhone app is just the icing on the IMDb cake, and as a free app it should be on the home screen of every movie fan's iPhone. Check out the gallery for screenshots of IMDb in action.