No regrets. I do buy a lot during the end of year sales (eReader.com, B&N-owned and fictionwise-operated), often buying 75%+ of my reading for the year that way; but like Karen, it's all planned out. I don't pay retail. I don't even pay retail minus the standard discount. If I see a book I want during the year with no sale, I wish list it. It's not like they spoil.
Which is not to say I don't spend too much on books, it's just that I can't write my over-spending off on impulse control. It's premeditated.
I was looking at some new authors this new years, and was happy to discover several series I was contemplating had their first book or two on the baen free library. Smart move on the part of the author. I'm already set on one of the series.