I was looking for that one as well in Montreal.
Every Mac dealer downtown I have been to claims they had them, but are now sold out and have no clue when more are coming in - they're on order is what I'm being told at the store.
I was going to go for the USB only version. Couple of reasons why -
From what I can gather from the specs, the USB/Firewire version does not provide powered USB ports, the USB-only does; also what is the advantage of a firewire hub? You can daisychain firewire, so one FW port on the Mini is sufficient, at least for most connectivities I would think.