So the October buyers get 1% + 5.75% (approx) for Oct - Mar, and then they would (currently) get 0% for Apr - Sep. The November buyers get exactly the same, but for Nov - Apr followed by May - Oct. Clear?

Not quite. The October buyers get 1.2% + 3.58% for a total of 4.78% for Oct - Mar, then get 1.2% + 5.72% for Apr - Sep. Whereas the November buyers got a 1% fixed rate, not 1.2%, so they're not getting exactly the same (the fixed rate changed in Nov).

That's why several of us chose to buy in October, rather than November. You were guaranteed 4.78% for the first six months, and 6.92% for the next six months. If the inflation rate results in a 0% rate for the third six month period, we can simply hold for 3 more months, then cash in.

I'll leave it to the math whizzes (which I definitely am not) to calculate what the actual APY would be when held for 15 months. (I suspect it's somewhere around 4.75%--not bad for the pre-tax equivalent of a 15 month CD)

These various scenarious were discussed back in October in this thread:

http://boards.fool.com/Message.asp?mid=23200241&sort=whole

2old