My retail store only had 1TB available, and plenty of them. I do wonder if they increased the size of the case for the 2TB, as I disassembled a 1TB case and there is not enough room for two 12mm drives in it. Unless there's now a 1TB drive that is ~10mm or smaller on the market.
My local Apple store (a regular-sized mall version) said they hadn't gotten any yet when I went today, so I just ordered a 1TB online, which should be here by the first week in October. My plan is initially to use it as an enclosure for 1 SSD (and keep one HDD in there too, I guess) and eventually stick in two SSDs in RAID 0.
If they made them, but I'm not sure they do. I know they have 750GB 7200 drives as I have one, but i'm not so sure about 9.5mm 1TB ones. I suspected this when I noticed that Lacie's 2TB was only 5400. I mean, why do that for a high end item like this? there's no power issues.
I have 2 750Gb 9mm drives I could put into this. But one of them is 5400. I suppose you could use a variety of options. But I think i'll just stick with the configuration they have. It's a good one.