Time to import a French 7.12 core translation into the database.
Time recorded to execute _locale_import_read_po() in _locale_import_po() (gettext.inc). Measurement using timer_start() and timer_read().
Variable number of translations exist in the database before the import.

NO PATCH APPLIED
  0 existing translations: 13927.85 ms
10K existing translations: 15782.94 ms
20K existing translations: 16740.98 ms
40K existing translations: 16299.71 ms
80K existing translations: 16252.54 ms
                         
MD5 PATCH                
  0 existing translations: 14400.30 ms
10K existing translations: 16049.62 ms
20K existing translations: 16001.27 ms
40K existing translations: 15977.60 ms
80K existing translations: 16051.21 ms