It was very challenging to work on 3.0 feature set and my team worked really hard to ensure release was as per schedule. Now that CiviCRM v3.0 alpha1 is out, I can shed some light on my favorite features in 3.0
Usability
- Navigation Menu, I bet this will help to reduce number of clicks needed to navigate inside CiviCRM.
 - “Create New” (Shortcuts select) and “Recently Viewed” blocks ( shows recently modified / viewed objects)
 - New work-flow for creating new or selecting existing contact while adding Contribution/ Participant etc.
 - New UI for Contact Edit and Contact Summary which can be highly customized by admin.
 - Eye pleasing look and feel by moving to more neutral color scheme.
 
CiviEvent
- New tab interface for Event creation.
 - Waiting list support.
 - Ability to use default / create event templates to simplify event creation procedure.
 - Administrator approval for participants and lot more.
 
CiviReport
- 22 default report templates which can be used to create custom Report Instances.
 - Ability to generate tabular/charts for a report, also automatically email reports via cron.
 
Other Features
- Multi-site Support: ability to setup single CiviCRM install for multiple sites.
 - Complete migration to jQuery from Dojo ( which helped us to reduce tarball size by 1MB )
 - CiviCase improvements / fixes.
 
Entire team is super excited about this release, which included 200+ bugs/features and I hope everyone from the community also likes it.
Complete list of features can be found at http://wiki.civicrm.org/confluence/display/CRM/CiviCRM+v3.0