The main Difference is in QTP9.2 we have options to import 
and export the object repository files

1.Instead of test menu in QTP8.2 we can associate library
files in file menu settings option
2.we can create and associate any no.of repositories to the
action.

in  9.2 we able to make video files as what we are 
recording...............

The main differece qtp8.2 maintains two typs of Object 
Repositories.Like Per-action and Shared Objct repository.


        But qtp9.2 maintains only one Object Repository 
like shared object repository

1.in qtp 8.2 we have five parts
1. active screen
2.datatable
3.testpane
4.tools bars
5.debugger view
but in qtp 9.2 we have seven parts
including above five and information pane and resource pane

2.option are interchange in qtp 9.2
3. look and feel things are changed

QTP 9.2 :
1)Object Repositories modes is local and shared 
2)Can call multiple Object Repositories in an single action
3)Object Repository Manager to manage all of the shared 
object repositories, this includes adding and defining 
objects, modifying objects and their descriptions, 
parameterizing test object property values, maintaining and 
organizing repositories, and importing and exporting 
repositories in XML format.
4)Built-in function library editor
5)Mercury Screen Recorder: Capture your entire run session 
in a movie clip or capture only the segments with errors, 
and then view your movie from the Test Results window.