1. we must know vb script
2.expertisation is required

QTP tool is not suitable to perform below testing types.
1.Usablity testing
2.One time testing
3.Random testing
It will not support all enviorments.
This tool is costlier.

mugambo.need to know vbscripting!! ,but its not a drawback 
of the tool !!
i would like to add few more points to the above answers
1 .....in qtp u cannot work on multiple scripts at a time 
like in winrunner.(again this is not a drawback,but not so 
frendly as winrunner in this matter).
2...... working with object repository differs sligtly with 
qtp versions.(may be part of enhansment).
3...... object spy is not so friendly as in winrunner.
 ----------discuss..

What evry qtp but dont attend any interview if Telugu guy
takes interview pl note this
point...............................................................i
am also telugu only thats why i am telling this

Hello Sima,

Wat u told.. i am not understand.. why u use telugu guy...

hello sima,

what u mean by telugu guy...questions, please think once 
before u write ok

i have a different answer

1. QTP does not support to check morethan one property of 
an object at a time.
2. it will not show the differeces between two images as   
in winrunner