Matrix,
Your solution is very simple and easy to understand.

Although it works fine for small to medium tables, or for tables with low access/update,
for very large tables, or tables with heavy access/update, it may:
1) Generate an abnormally long transaction.
2) Fill the logs.
3) Be involved with another process in a deadlock.
4) Run for a very long time.

It is also important to note that for large tables, the internals of your query will be
very ineficient as the system will store a rowid for each unique key and loop thru
each one for every row.

The best and optimized solution would be to write a program to loop thru each row
in the table, begin a transaction and commit every number of deleted rows -- usually
one to five thousand is very quick, safe and easy on the database.

Good luck!