The development of Custom Properties 0.98 was aimed in three directions: extend usage to other content elements, improve search results, SEF compatibility. While we where at it, we added other improvements in terms of usability and search engine "frendliness".

The following is an incomplete list of feature.

• tag articles
• tag third party content elements*
• tagging from the frontend
• tagging multiple articles at once
• tag access level
• tags appended to “meta keywords”
• tag in page title
• image thumbnails in search results
• drill down search results summary
• selectable search results format: HTML introtext, plain text, only title
• advanced search module
• selectable module layout : tables or divs
• restrict search scope
• access level for search results
• tag clouds module
• JoomFish compatible
• core SEF compatible
• sh404SEF compatible

* via plugins. BookLibray and Docman installed as defaults

Known issues:

Search by tag + core SEF = problems with on ASCII chars in CP fields:
In order to be SEF, you need to generate URL that "reflects" the article content. Someting like "http://site.com/name-of-article" or, in our case, "http://site.com/tag/name-of-the-tag".
The  problem here is that an URL can contain only alphanumerics and some punctuation, so, what to do if the tag contains accented letters or it is written in cyrillic or greek characters ? Various solutions are in place to adapt to those situations but core SEF doesn't play well with that, so your possibilities are two: install a third party SEF componet (sh404SEF works flawlessly) or set "URL format" to TagId in custom Properties configuration.