Transformers you will regret. The player, no. Even if HD DVD tanks (and if it does, it won't be for another year or so), your discs will still play just fine. And what did you lose? $160? Not even close to that, if you count all the free movies that came with it. If it bothers you, just enjoy all the exclusive releases for that format, and continue to buy the multi-format movies in BD. This format deal isn't going to be over for at least another year (I'd bet two).
For fuck's sake, at least you didn't buy a Wii.