First of all, i'm really happy with the filters it provides.
The drawtext allows you to burn timestamps in your video. I used it to burn it into my scene detection mosaic (see post below) so I can see at which time the scene changes.
The showinfo filter shows you some detailed frame information, first I was wondering why the (PTS) timestamps didn't match with the timestamps in my mosaic, but then (after a few hours) I discovered that the PTS timestamps are relative and can be changed to zero-baed with the "setpts" video filter.
The command I use to get a nice timestamped mosaic with scene changes and a log file that can be parsed to create a chapters file is:
ffmpeg -i $INPUT -vf drawtext="fontfile='/usr/share/fonts/truetype/ttf-dejavu/DejaVuSans-Bold.ttf':timecode='00\\:00\\:00\\:00':rate=25:fontsize=72:email@example.com: x=0: y=0",select='gt(scene\,0.5)',scale=160:120,showinfo,tile=10x16 -s 1920x1200 -frames:v 1 $OUTPUT 1> output.txt 2>&1
The problem is that there is no audio-filter which modifies the audio "frame" pts, so the audio-track is out-of-sync. There was a patch proposed in the mailinglist some time go but was declined because it share some code with the video-pts-set filter.
Then I found out that mencoder also does things like ffmpeg, so I simply tried to copy the audio and video stream and apparently the PTS timestamps are reset. There are a lot of issues though.
Apparently the mencoder libavformat muxing is broken for a looong time (I see mailinglist messages dated from 2008 with the same message), so now I try repacking it with ffmpeg or just get separate tracks and merge them together with ffmpeg.