A philosophical question about multi-platforming

[Hugo Jackson]

I've been using wxWidgets for a couple of years now. My hat off to  
the implementors and everyone else who helps make it such a great  
development environment.
My personal development approach is to first implement the  
application in wxGTK and after that's done move on to porting it to  
wxMAC and wxMSW.
I've just finished a frustrating three days of tracking down a bug in  
the wxMSW implementation of my current application which worked fine  
in wxGTK and wxMAC.
I have a wxFrame containing a sizer and within that sizer a wxPanel  
that I was periodically transferring a new wxImage to with a wxTimer  
method and OnPaint event method.
The problem turned out to be that the onPaint logic I had created for  
wxGTK didn't work in wxMSW, in fact it disabled wxTimer interrupts so  
that no timer events were being generated at all.
The solution was to insert an event.Skip() at the end of my onPaint  
logic.
For the most part there are not a lot of these problems when porting,  
but because when bugs do occur, they are often buried under lots of  
"working fine" code, making these kinds of bugs often incredibly  
difficult to find.
So my question is this... how important is it to the implementation  
team to have the different flavors of wxWidgets behave identically?  
Are these differences in behaviour important to implementors or  
should I simply adopt a more cautious approach to development, by  
testing my application more frequently and earlier on?
As I say, I'm not being critical of the way things are, I just want  
to be more in line with the wxWidgets multi-platform philosophy.