Main disadvantages:

* No system-wide file manager
* No videocalling
* Limited third-party apps availability
* No Bluetooth file transfers
* No USB mass storage mode
* 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
* No internet tethering support
* New ringtones available only through the Marketplace
* Swapping memory card requires hard reset; cards not readable by computer

http://www.gsmarena.com/windows_phone_7-review-521.php

How is it better than maemo?