I haven't heard anyone complaining about ones that it misses. I have seen a
couple of instances where removal of the keylogger was sufficiently complex
that even with Microsoft PSS assistance it wasn't neatly accomplished. I
believe it was possible to remove the keylogger, but it ended up leaving the
user without the use of the keyboard, which was awkward.
If you have a verified situation with one of these in place, I'd advise you
to call Microsoft PSS--it should be a free call.
I don't think it is possible for MAS, or any other programme, to detect and
remove all Keyloggers - the days of one programme being able to fight
spyware, malware, viruses are long gone.