NO REGRETS.
I was actually going to say Trine, but I bought that a few weeks back as part of the Frozenbyte collection. It's a potentially cool game absolutely ruined by awful, awful, awful, awful, awful, awful physics. I want to like it, but alas.
Now I haven't played EVERY game that I've bought, but I have played most of them and found most of them enjoyable, some far more than I would have imagined (Sanctum and A.R.E.S. in particular). Most of the games I haven't played did not have ticket achievements, but I'm pretty confident in all of my purchases.
Actually, I might regret not buying the four episodes of Winter Voices, so I may make an "under the wire" grab for them before the night is over. I'm weary now because the achievements in the game are busted but the developer apparently has a six pages of fixes patch coming pretty soon. Plus, I'd almost want to wait until the last two episodes are out and grab them all during the Christmas sale and play the game, ya know, during winter.