Key features:
- Premium mobile OS (high minimum hardware requirements)
- Clean, uncluttered interface with distinctive design language
- Easy and thumbable user interface
- Smooth operation with cool animations and transition effects
- A fresh start with no legacy support needed
- Backed up and developed by one of the largest software companies in the world
- Excellent MS Office mobile implementation
- Top-notch social integration
- Excellent cloud services integration (SkyDrive, Windows Live, Xbox Live)
Main disadvantages:
- No system-wide file manager
- No videocalling
- Limited third-party apps
- No Bluetooth file transfers
- No USB mass storage mode
- No memory card support
- No multitasking
- No copy paste
- Too dependent on Zune software for computer file management and syncing
- No music player equalisers
- No Flash or Silverlight support in the web browser
- No sign of free Bing maps Navigation so far
- No DivX/XviD video support
Sources
