While trying to get an idea of prices on advance purchase AVE train tickets on RailEurope's website (my actual dates of travel are not open online yet for advance purchase), I noticed a significant price difference between the non-refundable "Best Second Class"/"Best First Class" and the "Flexible Second Class"/"Flexible First Class" but the difference in price between taking first class over second class is negligible (around 15 Euro). Normally, I book second class seats, but might reconsider if I can get some feedback from those who have booked first class on AVE - did you feel it was worth the additional money?
I am comfortable booking the non-refundable "Best" v. the "Flexible" as my dates are set and the fare details on the flexible fare states it is only 85% refundable up to 2 days before departure and after that, there are no more refunds.
Finally, any thoughts on booking straight through Renfre v. RailEurope? I understand that there is a small booking fee involved if purchased from RailEurope's website, but I also hear some people have a really difficult time getting their tickets booked and printed from Renfre's site.