Re:
Hello,
...talldude meant encrypt your wireless network for security reasons. It doesn't introduce any performance benefits as such.
He's suggesting that if you have an unsecured network which isn't encrypted, then there may be a possibility that someone near you is 'stealing' some of your bandwidth by connecting wirelessly to your router.
How have you determined your download and upload speeds by the way? Did you use some kind of online internet connection speed test or program...?