The 1.1 release features a completely rewritten encoder, offering better performance and compression, and making more complete use of the format's feature set. Files produced by both encoders can be decoded by either release.

• Support for two-pass encoding
• Rate control fixes to smooth quality
• New encoder fDCT does better on smooth gradients
• Live-broadcast improvements
• Аdaptive quantiazation

download sources

BTW ffmpeg2theora has been updated for libtheora1.1

http://v2v.cc/~j/ffmpeg2theora/