hi,
i've been monitoring this problem since the n900 was released, and the suggested solution of mce.ini never worked (the file doesn't control the alarm clock vibration).
other than voting for the bug, there is nothing to do at the moment.
or of course find / write another program to use as alarm clock (one that doesn't vibrate).
I have 2 tweakr proflies loud/quiet. I use alarmed to automatically change profiles. When Im going to bed my quiet profile is activated which has vibrate disabled. This is my solution.
According to "strings" the file
/usr/lib/systemui/libsystemuiplugin_alarm_dialog.so
in package osso-systemui-alarm has "PatternIncomingCall" in it, so you could hexedit that file (and probably restart because systemui has it loaded) to change the pattern name to something else (probably keeping it the same length), and adding that pattern to mce.ini.
Sadly that libsystemuiplugin_alarm_dialog.so is closed source stuff so theres no real alternative.
anyone can help me? thx