Avidemux. It's just like VirtualDub, only with more formats supported and built-in codecs and filters. I always use it in preference; it joins AVC+AAC.MP4 files (without recoding) fine for me.
To join them in AviDemux:
File -> Open -> Select File
File -> Append -> Select File
Set all to Copy
File -> Save -> FileName
According to AViDemux forums, this join process is lossless (http://www.avidemux.org/smf/index.php?topic=9467.0)
SMILETRON - Disco Just Won't Cut It This Time
This video is made by combining the following two official gameplay video by the developer. I replaced the audio with the original high quality mp3. I also cut the last few seconds of the first video and the first few of the second video to make the transition smoother.
Waves - Official Gameplay Trailer
Waves - WIP Chase Mode Free Update