Would love to see the ability to freeze column headers at the top of the page when a user scrolls through a long list.

For organisations that would like to use Communication site as their intranet it would be great if you could provision the root site as a Communication site, rather than a team site with a redirect to the communication site.

There is a workaround as mentioned here but i'd prefer a Microsoft supported method https://hangconsult.com/2017/06/29/change-sharepoint-online-root-site-collection-to-use-the-new-communication-site-template/

Document Sets in modern document libraries

It would be helpful to have sections that collapse, tabs, or anchor links for pages that contain lots of information. Word allows you to create bookmarks, and OneNote allows you to create tabs to easily navigate lots of information on a given topic. It would be great if you had the same flexibility with a page in SharePoint

Please allow javascript customization and css branding/theming in the new document library experience. A custom cross-site navigation is one example that is used by many customers. Also many customers want their intranet branded in a different color but office ui fabric blue.
JSLink is also used very often. And don't Forget about all the third-party forms solution provider like Nintex and others.
The new experience provides many advantages, but without customizations it is just not usable for larger intranets anymore.

Please change how SharePoint generates links to uploaded documents and site pages, so that URLs with spaces will replace %20 with a dash instead. Most CMS tools including blogs do when generating SEO friendly URLs. Links with %20 throughout are too difficult to read.

This feedback site is a perfect example:

This:
https://sharepoint.uservoice.com/forums/282887-customer-feedback-for-sharepoint-server

is easier to read than this:
https://sharepoint.uservoice.com/forums/282887%20customer%20feedback%20for%20sharepoint%20server

I'd like to be able to resize an image directly from the modern pages image webpart. This is really annoying that the pages are so easy to create but that you can't control the image size on the page.

Please provide the capability to change the header of the new modern pages (i.e. the large banner graphic on which the title is sitting. It currently means page content starts half-way down the screen which isn't the best use of space.

The mobile views are not a solution, so many customers turn to custom design, but I would rather a responsive design be built into SharePoint.

Current term set based solution is not usable at all in real life multi site collection scenarios.

Column totals missing in modern list views.

This is an often used function, and the workaround to set the list back to classic will only be a temporary solution.

Including support would be needed.

My client has a legal requirement for using software, intranets that is Bi-Lingual.

Communication sites are really great way to building new Intranets quickly but this is a critical feature for adoption.

So Infopath 2013 is supported in 2016, but SharePoint really needs a full modern full-featured forms editor. FoSL looks promising but the functionality is not clear at this time.

The sync limit does not match OneDrive for Business, and adds complexity to the end user experience, administration and architecture of SharePoint. Please remove this sync limit.

Currently the default "Title" column does not have an adjustable width in the new modern SharePoint view only, classic view is unaffected.

So if the column contains 1 row and the cell contains very little text the column width will not adjust to fit the width of the text and leave a large empty space, pushing adjacent columns to the right off the screen.

I need to be able to check-in or check-out multiple files. I'm not able to do this currently, when selecting multiple documents.

The modern pages are great, however there should be more flexibility such as being able to select different page layouts and would take the best from the old classic pages and incorporating with the new modern look and feel.

I would like to be able to remove the header from the new/modern "Pages". When I add a new page on SharePoint online now, I love the new page except for the top header image and text which takes up about a 3rd of the page. It's wasted space and not aesthetically pleasing.