With Windows Vista we told ISVs "Hey - applications may break on Vista. You should test your application".

What some ISVs appear to have heard is  "Hey - other ISVs application may break on Vista. They should test their application".

I am going to try an alternative approach this time (tongue in cheek).

"Hey you. Yep - I'm talking to you. No - not that guy next to you. I mean you. Yep, you Mr ISV developer. Turn off your ipod. Let go of the mouse. Now read the following very carefully and very slowly.

 

Y o u r   a p p l i c a t i o n   m a y   b r e a k  o n   L o n g h o r n.  

Y o u   s h o u l d   t e s t   i t.

B e f o r e   y o u r   c u s t o m e r s   d o.

 

Thankyou."

And the good news is we have the guidance you need over at http://devreadiness.org, more specifically in the App Compat Cookbook.