What you are saying and yes it is a fact that it is not reccomended people flash with un-official firmware
There is no way this update will brick a N900 because its an OFFICIAL Nokia update albeit released in an UNofficial way so everyone can be rest assured flashing with the new update will NOT brick your N900 as long as you follow the easy instructions on this page.... http://maemofanatics.com/how-to-flash-your-nokia-n900/ IT WORKS 100%.