When you go to an editor's user page, the Edits table (under Statistics) includes a total for Failed. The count of Failed edits listed there seems to include canceled edits that were created after the NGS migration (but does not include edits canceled before NGS). However, clicking on "(view)" for Failed only lists actually failed tickets, i.e. does NOT include canceled ones. This is inconsistent; perhaps the best solution would be to add an extra entry for Canceled (and possibly include Canceling in it as well?).

For an example, go to
http://musicbrainz.org/user/dvornik
This claims there were 5 failed edits, but clicking on "(view)" shows none.