Advantage and Disadvantage of flex compare to other

I search but didn't get any duplicate question like here. So, i ask it.

I am going to develop one Web application, Desktop application and Mobile application. I am going to develop this application in Adobe flex.

But, my question is what is the advantage and disadvantage of developing application in Adobe flex and other platform.
May i go through Adobe flex or another? If in other than why?
What things i have to remember before developing the application?

Any help is appreciated.
Thanks.