Not sure why people say ZiPhoned iPhones cant be upgraded to 4.6. I just did mine a few minutes ago!
Its very easy to use. http://forums.overclockers.co.uk/showpost.php?p=11551730&postcount=221 Just go by the screenshot at the bottom of the page and hit flash and let it do its thing.
Top man! Cheers fella.
By the way, should we Boot Neuter with the original SIM or does it matter?