I pre-ordered my 64GB Transformer Prime back in November and I got it on Tuesday, Jan 3. I think they are still filling the backlog of preorders. I got mine from B & H Photo and Video. Their site now says the 64GBs will be restocked later this month and more 32GBs will be in in February.
How do you like your Prime? I've got the first Transformer, and had briefly considered upgrading. But I've heard some people have had issues with weak WiFi reception, due to the aluminum body interfering with the RF signal.
Banshee