Information_schema query taking more than 7 minutes

The biggest current problem that I know in the MySQL servers is the performence of information_schema. This is reported as bug 19588:

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1829 to server version: 5.0.22-max-log

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> SELECT TABLE_SCHEMA,
    ->   sum((DATA_LENGTH + INDEX_LENGTH) / (1024 * 1024)) as size_mb
    -> FROM information_schema.TABLES
    -> GROUP BY TABLE_SCHEMA
    -> HAVING size_mb > 10
    -> ORDER BY size_mb DESC;

...

xxx rows in set (7 min 34.71 sec)

Even though this server hosts a lot of data - more than 7 minutes for this query is tough.