iPad In Between: Not Smartphone or Notebook
Mobile Media Maven -
Secondly, the iPad can stream full-res online media in a way that the iPod, iPhone or any other phone cannot. The larger screen just puts the phones to shame, and the 1GHz A4 processor handles even the most demanding HD media files with ease. It's basically the bedside media viewer that you've always wanted, and it's way easier to grab than your full-size notebook. Plus, it'll play videos for 8-10 hours on a single charge; let's see your MacBook Pro (or any other notebook) do that.
Cracking The Books -

The App List Lengthens as Does Battery Life -

Finally, the iPad lasts for 10+ hours. The battery in the iPhone, and most every other smartphone, is lackluster. Even if you never make a call, and only use apps, 10 full hours of use is a stretch. The iPad can easily last 10 hours when used, sometimes more if you use it lightly. It makes sense, though; the iPad has two iPhone batteries working in tandem (basically, anyway), so that's certainly a plus.
Now, onto the comparison between the iPad and your notebook...