Do yourself a favour and hold out on the upgrade for at least a month (to be safe)... Some people are having issues with upgrading to the recently released Win 8.1 ... The version you ultimately will want to upgrade to.
And why not update to X3 whilst you are at it.
Also please audit your hardware/drivers to see if it will work on 8.1... Again a scenario that should stablise within a month or two.
Of course some people will have no problems....