The apps on the iPad are just downright awesome. The iPhone and other phone apps don't even compare. I got mine originally to do mockups and brainstorming sessions with clients using various apps like Adobe Ideas, iMockups, Index Card, SimpleNote, and iThoughts HD. And I use an app to invoice clients from the iPad while still on site. Projects are managed with Things for iPad by Cultured Code.
Flipboard and Instapaper on the iPad are worth buying the device all by themselves. And Airplay from the iPad to the Apple TV is probably my favorite feature. Browse content on the large display with a very nice interface, tap a button, and the video is on your big screen HDTV and surround sound system.
Then there's Garage Band, iMovie, Netflix, EyeTV, Air Video, Hulu Plus, Infinity Blade, Real Racing HD, and I could go on and on just looking at what I have on my home screen.
This is by far the best entertainment device I've ever owned. If I had to choose between my PS3, my HDTV, and my iPad and could only have one of them I would choose the iPad with no hesitation. Internet, email, TV, apps, movies, books, games. etc. all enjoyed with a better and more enjoyable experience than my Macbook Pro or iPhone 4.