My only regret is not spending my life savings on Bitcoin back when I first learned about it, when it was going for $15 a piece.
Oh well.
Yes, me too. Not buying/mining when it was much cheaper.
The worst mistake I made with BTC was lending it out on BTCJam about a year ago. I got my money back, but because the loan was denominated in USD, and because BTC rose during the life of the loan, I got back less BTC than I lent.