This is in each MC11 build thread:
CUE file playback support with sample-accurate MP3 seeking
Many Theater View enhancements
Split views so you can look at two (or more) views at the same time (ex. look at Media Library and Playing Now together)
Vastly improved database engine capable of handling 100,000's of files and large amounts of metadata (lyrics, bios, etc.)
Several memory and speed enhancements -- like database and skin unloading when minimizing MC
Much of MC's interface can be translated to other languages
Integrated database import and update with smart broken linking repairing, and other nice features
MC can run with guest permissions on Windows 2000 / Windows XP
New view customization system with more flexibility for thumbnail size, text, etc.
Options dialogs reworked -- several small options added
Added multi-zone synchronization
Added Album Gain support
Document support with full text searching / indexing
Pane auto-sizing
Tile view that allows fully customizable Track Info style tiles to be used in file lists
New database caching layer that makes a huge speed difference in many areas of MC
File tagging happens in a background thread so MC can continue to be used while it's saving tags
Basic image editing
Enhanced album grouping for pictures so pictures taken together get grouped without any user intervention
Preview mode to only play the intro of songs
Video CD playback support
Audio resampling uses Shibatch's high-quality SSRC filters
ATI HDTV card support
Hauppauge WinTV PVR 150 support
UPnP device support
Audible.com Store -- full integration (downloads, playback, bookmarks, etc.)
Sony PSP support
iPod -- Support for multiple iPods with different profiles
New file format -- Shockwave (SWF)
RAW image support (crw,cr2,nef,mrw,orf,raf,pef,dng,srf)
Multi-channel support (5.1, 7.1, etc.) for WAV and WMA files.