Advantage-
  • Good User Experience, close to a Windows GUI
  • Much easier to use than plain JavaScript
  • Impressive speed
  • Coders don’t have to worry about Browser differences
  • Reduces Server Load as fewer round-trips
  • Widely used, good community support
  • Many components already developed
  • Open Source

     
Disadvantage-
  • You probably still need a Server framework for initialisation and Session management
  • You need another app to supply your data (like a web service) written in another language (like .NET, Java or PHP)
  • In larger apps, slower to code than PHP or ASP.NET
  • You need to understand CSS
  • Can still be difficult to debug, especially if scripts interfere with each other.
  • Source code is difficult to protect