Yeah, for richer formatting, we'll definitely want an XP solution.  Later.  
Even now, I'm not sure we can do without formatting entirely, though.  The 
current read-only preview isn't completely unformatted -- it changes the 
color of the misspelled word in context.  
  On GTK, this capability is built into the basic editable text control.  
  On Win32, we have to switch from an edit control to a rich edit control.  
Any ideas on how we should handle this now using existing BeOS widgets?  
If there's no good way for you to vary the color inside an editable control, 
I suppose a reasonable BeOS-specific workaround could be to put a read-only 
copy of the word after the prompt, perhaps in a different color.  Forgive 
the ascii art:
  Not in Dictionary:   frazzzled
  +-------------------------------------------------------+
  |  This spell check stuff has me totally frazzzled,     |
  |  because I like to make everything pretty.            |
  |                                                       |
  +-------------------------------------------------------+
  Suggestions:
  +-------------------------------------------------------+
  |  frazzled                                             |
  |                                                       |
  |                                                       |
  +-------------------------------------------------------+
What do you think?  It's not as good as having the color change in context, 
but should still work for now, especially if you set the cursor inside the 
edit control to just after the misspelled word, so folks can locate it more 
easily for editing.  
Paul