Just bought Ulysses (and waiting for serial number!) in the meantime, want to report that in both 2.0.3 and previous version, no excerpt shows up in the Notes & Except pane. Tried trashing preferences, installing a fresh version — is this a bug?
The excerpt is initially empty - you can put whatever text you want in there. Ulysses does not create an excerpt on its own, but you can use this field for whatever you want.