I tried to update mine to FW1100 yesterday, i'm now the proud owner of a £700 doorstop...
I knew there was a chance of bricking the unit as some 'A' versions like mine have mainboards which can be fried during the upgrade, got as far as updating the gateway and hit the infamous '10% gateway Error 202', unit is now buggerred lol!
Imo, unless you are trying to cure any bugs the existing unit has (mine was randomly asking for the code and not auto restarting the nav route after the ignition was off), then i'd not bother lol
Off to find a new unit on ebay....