[Twisted-Python] UDP vs TCP for bittorrent-style file transfer

Hi list, I'd like to revive a topic touched on in the past. I'm playing with python socket programming and decided I want to make a simplistic bittorrent clone that uses UDP instead of TCP. My main reasons for the protocol choice are (1) I don't need guaranteed in-order delivery, and (2) I need to get around NAT restrictions without making the user manually forward ports. Couple questions... 1. Are those good reasons to ditch TCP, or am I being an idiot? (Always a possibility.) 2. Even though I don't need TCP's in-order guarantee, I still need an ACKing mechanism to make sure all the packets eventually arrive. Is there any (simple) code written that accomplishes this with UDP?