I cleaned up some phrasing and made some corrections - most importantly, Stepmania lets you increment BPM / Stops / whatever by .001 if you hold the Alt key.  If you've upgrading to SSC / SM 5, they've added even cleaner ways to go about it through the "Edit Timing Data" options under the Enter menu.

Given my distaste for stuttering, I haven't had reason to test this, so I didn't add it to the article, but SSC (and possibly OpenITG, SM4, or older SM builds - I haven't checked) has "Convert to Pause" and tempo multiplication in the Enter menu - so perfectly synced stuttering may no longer require math and awkward manual precision.

The Pause:
1. Hit Space
2. Move down one 32nd note
3. Hit Space, Enter, "Convert to Pause"

The Speedup
4. Hit Space
5. Move down to the next step (one more 32nd note).
6. Hit Space, Enter, "Tempo" -> "Expand 2x"

These steps assume you want to stutter 16th notes with 2x BPM.  To use 1.5x, I believe you'd want the pause to be one 48th note, and you'd use "Tempo" -> "Expand 3:2"; 3x would be two 48th notes of pause, then Tempo -> Expand 3:2 followed by Tempo -> Expand 2x (there's no Expand that does more than 2x, so you have to chain a 1.5x and a 2.x to get there).

Also, posting the link for quicker access from this thread: http://www.pnwbemani.net/articles/how-to/pefect-stopsstutter-gimmick/52

Thanks for fixing it up a bit tony!