Whatsapp Web may not be as good as you think

Reasons : 

• iOS devices do not support this feature. Only applicable for Android, Windows Phone and Blackberry users
• When your mobile phone does not have battery, Whatsapp web does not function
• You can only use Google Chrome browser and not any other browser
• You cannot delete any conversation or even edit your profile and status while using Whatsapp web You cannot start a new group chat using this feature
• It will only work if you have internet connection for the phone while using this feature

Source from http://www.credencys.com/blog/know-the-pros-and-cons-of-whatsapp-desktop-version-before-using-it.html