I really like ogv (og-Video, ogg/ogm Containers, Theora and Vorbis encoded video and audio) and Firefoxs ability to play them natively.
Flash often becomes unresponsive, bugged, stuttering and even managed to crash my firefox more than once so it couldn’t restore tabs.
The easiest way to convert your video is to just drop your video file onto (on windows) ffmpeg2theora-x.exe
When I converted a Trackmania video however, I noticed a severe pink-tint.
Note: This was with the snapshot/beta release/version of ffmpeg2theora named ffmpeg2theora-0.24-thusnelda.exe.
So this issue will probably be fixed.
Anyway, here’s shots from the video from original (uncompressed), Theora (default quality 5), Theora (quality 8 of 10), H264 (limited bitrate was 1000)