Hi,

There are a lot of new features added in odoo 15. If you ask top features, i can say that, it will be the improved Discuss App in Odoo15.

Discuss app in odoo 15 will be coming with added features like Voice calling, Video Calling and Screen sharing option. I guess this will be the highlight. And there are many other features like Improved user interface for odoo 15.

See the working here:  https://www.youtube.com/watch?v=zIc3MIB8yWo

Also many new improvements has bought in the website builder like gradients, shapes for images and website configurator for configuring the website on installing the website module.

Website Configurator:  https://www.youtube.com/watch?v=7dRKMxeOEg0

Improvements in POS

1. Ship later option
2. Customer Notes
3. Customer Display Screen
4. Coupons and Promotions

The import screen has revamped, and make it  more user friendly:  https://www.youtube.com/watch?v=XwWpTv8FjCo

New Editor has added in Odoo15, see: https://www.youtube.com/watch?v=gbLyGPD7mdM

Technical Features:

1. Code Profiling Option
2. Updates in Scheduled Action/ Cron Jobs
3. New Models to Manage Assets from UI
4. New composer mixin for wizards
   

United States Localization to pay vendor using ACH/NATCHA in Odoo 15.

Spreadsheet Updates

1. Odoo 15 Spreadsheet Supports Real-time Collaboration.
2. Download Option For Spreadsheet
   
   

Also  For More you can refer to my previous answer here to this question: https://www.odoo.com/forum/help-1/odoo-15-features-roadmap-what-are-the-expected-features-of-odoo-15-179466

Also checkout this Videos Introducing the different features in Odoo15:  https://www.youtube.com/watch?v=UJV8Cy4_7Iw&list=PLqRRLx0cl0hpQs-pVp_V6jOq_joZYLefk&index=1

Accounting:

1. Default Payment Reference
2. Company Data & Partners:  Similar modal windows for company data & partner have been harmonized.
3. German Localization:  Localization for Germany with German tax report submissions to Elster.
4. EC Sales List:  The EC Sales List report replaces redundant versions of each country meaning less menu items within multi-company environments.
5. Record Filtering:  A scroll down bar is added in filters when the list of records to filter on is too wide to be displayed on the screen.

eLearning

1. Frontend Section Deletion
2. New Filter:  Congratulate attendees who've finished your course with a new filter on the attendees list.
3. Tags URL:  Cleaned up tags URL
   
   

Events

1. Prefill Attendee Info
2. Sponsors:  Handle Sponsors and Exhibitors without needing to activate tracks.

Website

1. Background Videos:  Added 12 suggested videos to make choosing a background video easier.
2. Carousels:  Now mobile friendly! Now featured adapted style, centered images, etc.
3. Web Logo:  Added a new default website logo
   
   
   
   

Thanks