I have to disagree with this article on three points. The idea of creating a second administrator account, then turning your existing administrator account into a standard user account is incorrect. The second account you create should be a standard user account. Then if necessary, transfer your data from your administrator account, to the standard user account.
I do however agree with using a standard user account for everyday use. Apple has made it quite easy to administer your system from a standard user account. The two major differences you will see are, one, you will need to supply a administrator name and password to make system wide changes. Two, if you need to use the sudo command, you will need to su into your administrator account first, that or modify your sudoers file.
FileVault encrypts your entire user directory, this will use system resources, and if you forget your Master Password, you loose access to your data. I can think of better ways to secure data.
What about the built in Firewall on my Mac?
Oh, you can turn on the Mac's own firewall if you want. I have been running my Mac for over a year with out the system firewall, just to see what might happen. So far? Nothing's impacted my Mac.
Go through all the trouble of securing your Mac, and then leave the firewall turned off, just to see what might happen? Makes no sense. If your behind a router with a built in firewall, your already protected and can leave the firewall in OS X set to allow all incoming connections. But if your using OS X in another fashion, lets say in a public wifi setting for example, I would recommend selecting a more secure setting.
