This is a great question and comes up each year. Last year I pre-bought Hamers (very early- March) Hot ones for $175 a ton, however this year that same pellet from that same store was $285 (pre-buy).
So what to do? I will will pre-buy half or less than my anticipated need for the winter of 09-10 and look for better deals durring the season. I believe pellets are at an inflated price at the moment and will possibly decrease during the heating season.
Why do I think this? Simple- pellet stoves are not a tremendously economical option when pellets are @ $300+ a ton and oil is at $2 a gallon. Also last winter represented a pellet stove craze because in the summer oil was $4+ a gallon, pellets and stoves where in hot demand. I believe this year we will see a dip in demand as many of the pellet newbies of last year give it up because of the work and lack significant savings because of high pellet prices.
My prediction- look for a glut of used stoves on ebay this summer and declining pellet prices through out the year.
Disclaimer- This is just my opinion and could be totally off, so take this with a grain of salt.