The dev-team have updated redsn0w with a couple of fixes.
First, it doesn't give non iPad users the setting to select what the mute switch does any more - LOL
Secondly, it gives you the option to have an animated bootlogo again, just like we had on 4.2.1 with Greenpois0n - YAY!
More details at the dev-team blog.
It should be safe to run this over the top of your jailbroken device, however you MUST NOT select the "install Cydia" again!
If you don't want animated bootlogo functionality there is no need to run it at all!
Fill yer boots!