I am curious to find out how useful Android would be for turning my Sony Vaio dual core laptop into a user friendly internet portal for light entertainment and basic tasks, such as diary keeping and list making. I like how simple Android makes installing and running apps on tablet and smartphone devices, without any difficulties or requiring special knowledge. How easy is this to achieve through Linux, without having Windows installed?

Thanks in advance.

Not great, imho.

You keep being obstructed by the fact that it thinks it's on a phone, or mebbe tablet. For example, you want to send a file to someone; but you can only attach a picture, video, or sound recording to the email.

You don't need Windows or Linux to install Android (well, apart from to create a bootable disc or USB stick) -- it's an operating system.
I've loaded it into a virtual machine using VirtualBox and it actually seems like it could be usable with a mouse and keyboard but since it can't be made to go full screen in VirtualBox due to lack of drivers I couldn't test whether it would feel any good day-to-day. However, as business_kid points out these phone and tablet operating systems are locked down in strange and arbitrary ways which could make them frustrating to use on a day-to-day basis.
If you are interested you can find out more about running Android on your PC here:
http://www.android-x86.org/
You could also take a look at Chrome OS the OS that Google developed to run on more traditional laptop devices.
http://getchrome.eu/download.php
(Thanks for bringing this up you reminded me to take another look at ChromeOS myself)

You can send any file you like from an Android device. It's not that hard, you just have to know a tiny bit about the OS and how to use it. Android for x86 isn't really ready yet, though, AFAIK. It was designed to run on an ARM device. You can buy an ARM computer that will run Android pretty cheaply, although they tend to only come with the bare box, and you'll need to add a keyboard, monitor, and mouse. If you have those on hand already, you can get a media machine or whatever up and running pretty quickly, for $50 or less. Many come with Android preinstalled, perhaps on an SD card. Google will find many of them for you. Understand that Android and Linux aren't exactly the same things, even though Android does use a Linux kernel.