Can't answer it directly other than to say the whole design and presentation setup was changed. If you've not been reading the forums, you may have missed a lot of discussion about installing the new module over an existing one. For one, the new module now has its' own table to store settings, which includes 3 default xsl templates.
Previously, the news module allowed for custom xsl's to transform the newsfeed source, and this is still possible with this very important provision - the newsource is transformed to a RSSv2.0 news format, which may or may not be successful depending on whether your news source was following the specs for their particular format, atom, rdf, rss091, rss1.0, rss2.0. With the new logic any feed that cannot be transformed to a valid RSS2.0 format cannot be used with the new module. Custom xsl's cannot be used to overcome that limitation.
At least you still have the custom xsl files in the portals/n folder.
Yes, it is a real problem for a lot of folks. Your alternative is to use non-standard newsources with their custom xsl counterparts in the XML/XSL module. If you have a lot of feeds and sites to manage, this is more than a real pain.
The bottom line - don't use the new News module on a Production site until you've tested it on a Non-Prod site to see the level of work you will need to do to make it work. There are other issues, as well, like caching times, and using more than one News module on a page.
All of the issues are being sorted out by Peter, but if you do see something not quite right, do everyone a favor and log it into the issue tracker, so it can be worked on.
Cheers