I have carried out some more testing. Sorry for the time lag but I only seem to get time on weekends nowadays. Your suggestion of using Match Case is really not usable since in most cases I don’t really care about the case of a search / replace string.

In my testing the target file is a plain text file with 1 million lines (137 Mb)

9/05/2008 19:30 137,109,008 target.txt
137,109,008 bytes in 1 file and 0 dirs 137,109,504 bytes allocated

The host is Windows XP SP2 with 2 GB of ram. I am replacing the word Feature with abcD – 7112 occurences. I have carried out the test with three editors; Textpad, Notepad++ 4.8.5, and emEditor v7.00.5. I carried out the tests several times and then averaged the results. As you can see Textpad is the outright winner. Its no case matching search and replace is actually faster than emEdit with Case matching. At the moment Textpad gets my vote.

Textpad 5.0.3 32-bit:
No case matching: 5 secs
Match case: 3 secs

No case matching: 47 secs
Match case: 14 secs

EmEditor v7.00.5
No case matching: 36 secs
Match case: 7 secs