The login_detector patch is only a couple of lines of code and it works like a charm against the recent bot-net attacks.
Read the thread on the SMF community forum and you see lots of happy users.
As far as other mods go, I used to use
reCAPTCHA and the
Stop Forum Spam mods but they really didn't seem to be very effective so I removed them both.
The best I've found is the verification questions mod. If you come up with good questions, it stops spammers in their tracks. Incidentally, I think that verification questions are a standard feature in SMF 2.0 (currently RC5, I think).