Take some time to learn what you have first. You may be satisfied and if you just got yours, it will have the latest official update. I'm not saying that all of the leaked OS's are bad. Just saying that sometimes you need to be a bit more experienced with them to get things to work in your favor.
TL/DR - if it ain't broke, don't break it because you can lol.
Some of them can make the phone run faster but it depends if you have one that is official or not. I'm honestly not sure of the newest version. The OS's are free, you can usually find a link to beta OS's here and also on blackberry.com
Posted from my CrackBerry at wapforums.crackberry.com