The new features do not seem to be major changes but they add functionality and ease of use to the Catalog. Some of the changes implement features that were previously available in the old catalog. Here is a summary of the new features quoting from the post:
When you do a place search, the Catalog results now show an extended explanation of the parts included in the general geographical area searched. As stated in the post "the new catalog also shows new place notes, the “also known as” place names, and the “part of” places and “places within,” as the old catalog does."
Displays the Main Author in Bold Type
The Catalog displays any authored work with the main author displayed in bold letters.
Names of Catalog Searches
The names of the available catalog search categories are now the same as they were in the old catalog.
There are some places in the Catalog which do not contain any titles. The Catalog hides these places instead of letting the users conduct a place search for a place that will have no results. This particular change is not completely beneficial since it reduces the utility of the Catalog as a Gazetteer. I think hiding the categories is not as important as knowing the subdivisions even if there is nothing in the Catalog about that place.
Display Order for Volumes and Issues in a Serial Periodical
You can now see the bound volumes and issues presented in the order specified in the computer system that is used to create and manage the catalog. This system is called the OLIB and is a major library information management program and part of the OCLC.
When you conduct a title search, the system now finds your search term in subtitles. Previously, a Catalog search looked only in the titles. If your search includes a year, the Catalog will also search the “inclusive” dates, but you must enter either the first or last year. The Catalog will not find a date in the middle of an unspecified date range and will consider an individual year to be either the first or last year of the range.
Almost all of these changes are helpful. Some give more information than you are looking for but that is not always bad and may be beneficial.