Ok, I just managed to get the speedster ach with a time of 18:01.53 minutes. I found out some things that may help out other than the obvious "keep the stack low" and "back to back to back tetris mania."
This game has something odd about it that I couldn't put my finger on, until I was sitting there watching how many lines I had left to clear when doing various things.
Old school tetris clears 4 lines at a time with a tetris, but this game gives 8-12 depending on if you back to back them. Also, a 2 line T-spin clear gave me a 12 line clear as well. While it doesn't actually clear the field of 12 lines, if you watch the lines meter, it takes off 12 lines. Also, clearing more than 2 lines at a time AND combos will clear more than a single line as well. So the secret is NOT to score single lines fast, it's clearing as many as you can at once and trying to do the fancy T-spins.
This and practice will help you to net this tough ach. Good luck!
Phear my Uber Gimpyness!
RRoD #1: 9/27/08