Random details I've noticed in 11:
- File icons now show a preview of the image itself.
- The fill command, as well as the transform commands, have been moved from Effects to Edit.
- Color management now seems to be on by default. (Can be turned off by clicking the monitor icon in the file window. I'm not sure how to turn this off globally. You may need to change your settings to make sure the colors are consistent across programs, if you use Photoshop or other graphics programs that use color profiles.)
- Recent files have been moved up in the File menu, below open. 
- The welcome screen can be turned off/on.
- The program checks for updates online at start; this can be turned off/on.
- The polygonal selection tool can be used to make irregularly-shaped selections as well. 
- Hard Media controls seem to interfere with some brushes. It doesn't affect all brushes that HM settings could affect; it's only a few brushes out of hundreds. Will look further into this; it may just be a matter of settings interfering with each other.

All of this is aside from the notable updates/changes (check the Corel website for changes between X and 11). There are probably things I've missed due to not using certain tools often. 11 does seem to run a little faster than X for me, but as noted by Corel, that's probably dependent on one's computer etc. 

ETA: Forgot to mention, the new "real pencil" brushes look very good. They're not 100% realistic, but they come pretty damn close.