Well Rudy, I would say its slightly faster, and my battery life is longer (slightly)
BUT, the real reason why I would want to update is this, it's an up to date iOS that is Jailbreakable (for now) so at the very least you are going to be running an iPad on the latest operating system.
The only problem is, you may lose some of your Cydia apps from the 5.1.1 Jailbreak, this is because some apps are still be updated, so I would possibly make a note of your free Cydia apps, as these aren't stored within Cydia, once jailbroken go through the apps one by one, checking to see if the info remarks on an update to iOS6, this will save time with crashes because of conflicts etc
I hope all goes well if you choose to update Rudy, come back and let us know how you get on.