Just to make an overview of SharePoint 2013

1. Major changes on UE. More AJAX is incorporated. Things like Site Setting. No more Traditional Page Refresh.
2. Office Web Apps is no longer a service application. That means, the installing of Web Officer Apps is separated and can be shared for Lynch and Exchange.
3. eDiscovery capabilities, support for searching and exporting content from file shares, exchange and SharePoint. Team folder can be extract and shared via Exchange.
4. Web Analytic is now part of the search. Click through rate is integrated to enhance the preciseness of search. Things it tracks is like People who view this item also view other item.
5. SharePoint theme is now based on HTML. Designer can make use of this HTML and render back  to MasterPage and etc.Additionally, SharePoint 15 provides “Tri it Out” feature which you can see how the new theme looks. Note: PowerPoint is no longer used to create custom theme.
6. Web Part is now rendered using DIV! no more TABLE =)
7. SEO friendly. In term of SharePoint URLs.
8. Feed is enhanced to allow user participating, like putting # tag. Design for My Site is much more simplified now.
9. Search. Personalized search results based on search history. Previously searched Content will be promoted. Previewing of content is enhanced as well.
10. Excel BI. Instant analysis through in Memory BI engine.
11. Excel Services. Improved data exploration. User can easily explore data or report. User can point the value in chart or pivot table. Comments for drill down is supported. Calculated measures and members.
12. Performance Point Services
    1. Enhanced Filter and search
    2. Dashboard Migration. Dashboard can now be exported from server to server!! User can create the dash in Staging Environment and then exported to Production.
13. Visio Services is now allow more data sources. Comments on Visio drawing can be added directly to the file for discussion =)
14. Mobile Agent auto redirection can be turn on/off. (SharePoint 2010 will always redirect user to Mobile view first … and this feature is not really useful, personally)
15. Services does not compromise performance of SharePoint. As they are not actually sit inside SharePoint now. They are patched outside of SharePoint.
16. Major enhancement for Request Permission feature in SharePoint 15. Previously, user can only request access to the site collection admin. They couldn’t request on someone’s behalf, they couldn’t check the request status as well as all the sent requests. With SharePoint 15, the user is now able to send Any Permission Type (including those that the request current’t does not own) request to site collection admin. Also, the requester is able to view the existing users who is also with the same permission and etc. Admin would then be able to response the request with comment in conversional manner.