Yea, AviDemux is very nice. You load up the file you want, being a mythtv .nuv or avi or whatever. Then use the frame seek buttons or scroll to the points you want to edit out or cut or join or whatever. When you done editing the video you save the edit list. Which is great because it does not affect the original video at all so if you mess it up you've harmed nothing. Then you reload the edl edit list and setup your video and audio codec and filters (many great options) and save the video and audio and then you can use mjpegtools or transcode to join the files together.
What I got working now is I can batch process many recordings at once while I'm at work with a nice little script I wrote. If anyone is interested I'll write out the details and post the script.
Also avidemux's website has many helpful walkthrough's and an active forum.