Will the prices for Eurail passes hold constant through the Spring of 2010? Is there any advantage to purchasing them before the New Year?
In my experience, the prices of Eurail passes don't change drastically over the year, usually only if there is a big change in the USD/EUR exchange rate. The price will probably stay the same, might go up, might go down. Unless you know something about the foreign exchange rate, there is probably no advantage to purchasing (or not) in advance.
It is probably more important to make sure that you actually need the pass. What was once a "no-brainer" decision is now fairly complicated.
Peter, if you go to the "Railpasses" tab at the top of this page, then check out the "Railpass news" in the far right column, you'll find that several passes will be going up by a few percent.
I too have been weighing the convenience (while in Europe) of a railpass vs buying point-to-point and this time there is really no question...P2P is definitely worth the savings for our trip.