In the particular case of wxSmith, I daresay that your judgement is entirely unfair.
Actually, it is not a judgement, but an observation. The workspace keeps forgetting to redraw or draws a dark square. If I can't see the controls, it is indeed unusable for me. I must add I am using the nightly builds. Don't know if that matters, but you might be using a different wxSmith altogether.
Anyway, I hear the author is working on something new, so he must have felt there was room for improvement as well.
As for now, I have been trying wxFormbuilder for a while now and it gets the job done very well. No crashed yet. I can keep Codeblocks and wxFormbuilder open at the same time, make an adjustment in wxFormbuilder, rebuild in Codeblocks and see the result immediately. I can even open the XRC file
One thing I have not been able to fix though is that the dialog is 'pushed down' by the title bar, making the bottom 'drop off'. And I have old style (non-XP) controls. Whereas wxSmith displays a preview of the same XRC just fine.