I would ideally render with compressed avi (just to get the size down for videos that are often 40 seconds or a minute long) and uncompressed audio. Wav or aiff would be fine. None of the options in Pitivi that include Raw Audio seem to work properly - a video will render but plays back silent. Someone on the Ubuntu forum has said about Ogg Theora and flac audio, but though that looks and sounds great it's not easy to share on e.g. YouTube where those formats aren't supported yet.
Because I love subtlety I don't have any use for effects - subtle fade transitions are already possible that more than suffice - and would prefer, myself, the codec issues like this to get more attention.
Thanks for your time.