A new firmware update has been released for Microsoft’s Surface RT. It should pop-up on your Windows Update screen but, before you click it, bear in mind some aspects drawn from users' experience.
The most common of issues is that the tablet heats up to the point where it will shut down to prevent hardware damage. That wouldn't be very pleasant if you are in the middle of the update, so try and cool down the device (going inside a ventilated room should do the trick).
Another user claims that the Metro UI doesn't work after the update. That might be wrong, but it's worth taking into account.
If you encountered the random dimming issue, don't expect it to be fixed with this update.
On the other hand, some users claim that, after the update, their device is running more smoothly or, at least, that’s how it feels like. Also, the app transitions seem snappier and the IE performance is faster.
As of this moment, everybody is waiting for the changelog, so Microsoft, if you're reading, do release it.
Microsoft Surface RT Firmware Update - What the Users Are Saying
A new firmware for the Surface RT has been launched, but release notes are still pending