Being able to enter language sensitive colorized code is excellent.
However having created such a box there doesn't appear to be any way to return the for Format Code Block dialog with the existing source in place. It would be nice to be able to do this. You can just cut'n'paste but it looks strange since having highlighted the code to edit to copy it, launching the Format Code Block shows the highlighted content as HTML. You then paste over that 'HTML' and reset the language combo.
Being able to indent with tabs would be nice also.