Heyey, Speed Hibiki just happens to be one of my favorite characters in that game. Yes, she's hard to learn, but I like her better there than in Power.
Why? They both are very similar, it's just that I love the chain combos (makes up for less damage, and makes good combos easier to land) and her super-cancel in Power is damn near useless (not like, say, Kagami's).
Plus in Speed she has an awesome and useful 70% damage combo w/ a full bar: First, parry something. Then immediately do a DP+C. Right after that, do d,d+A then (A, B, C, d+C, A, d+C, f+BC). If your life is high, the best you can do after that is a standing or jumping B. However, if your life is flashing, you can finish the combo with her DM, which gets you the 70% damage. That one's a good crowd-pleaser. <IMG SRC="smilies/smile.gif" border="0">
Oh yeah, and she is really really cool. But Setsuna is the best. <IMG SRC="smilies/biggrin.gif" border="0">
Josh the FunkDOC
From what I've seen of myself and other players, Speed's the popular mode to use her in.