Three suggestions:
1. Add a snippet with the search terms highlighted
2. Show the date bookmarked in the result list and (if possible) the date of the last update.
3. Document the query language for extended queries
Two questions:
1. Do you reindex bookmarks after some time?
2. What indexing engine and platform do you use? (lucene/java?)
One remark:
1. The Chrome extension is unable to bookmark sometimes. The bookmarklet is working great.