If there's one thing smartphones have done, it's reduce the need for other things. Mp3 players, cameras, and even flashlights have been replaced by the little rectangle in your pocket. But is it enough to fully replace a computer? I'll tell you, but only if you continue reading.
Research
If laptops killed phonebooks, then smartphones dug the grave. (Wow, that was dark. I'm sorry. I’ll lighten up the rest of the article.) You no longer need to look through page after page for places to eat when you’re hungry. Your Android device will be equipped with every possible way to Google pizza places near you. After all it is made by, well, Google. So looking up restaurants, locksmiths, and handsome article writers has never been easier. Even deeper research for papers and articles can be done with a bit of navigating around the browser's limitations. And yes, you have permission to reference the articles of handsome article writers.
Streaming Entertainment
There are tons of resources available to you when it comes to video and audio streaming. YouTube, Hulu, Netflix, and Spotify all have great dedicated apps. While Amazon Prime Instant Video is yet to make an appearance on Android phones, I imagine it won't be too terribly long. However, you may miss out on some sites where the content is exclusive, such as web shows and podcasts without dedicated apps. You can’t always have your cake and eat it too. (Although, why would you get the cake in the first place if you weren’t going to eat it?)
Productivity
This is where the road gets a bit bumpy. The amount of productivity you can achieve on your phone depends on what exactly you need to do. (Especially with something as complex as video editing.) If you just need to take some notes, that's no problem. But if you're looking to fully write and edit documents, it may be a bit tougher. Don't get me wrong, there are tons of office apps available. But, unless your Android phone has a keyboard, (what it this, 2006?) you won't be able to type and edit the way you could with a standard keyboard and mouse. While the Android's Swype feature makes it much easier, you may still find it tough to type quickly. Unless you’ve got more than one hand, in which case high five. To all your hands.
Bottom Line
While your Android device is capable of plenty, it may never be able to match the abilities of a laptop. However, for casual users simply looking for a way to watch cat videos and Google how to find more cat videos, a phone or tablet will do the trick. However, if you’re looking at more expansive writing, editing, and even video work, a laptop will be needed. Or you can forget all the technology and just enjoy nature. Just kidding – unless the nature you’re going to has WiFi.