the ford stock DIS is a great unit. MOst people see minimal gains with aftermarket ignition unless they've gone FI. THose that have done this (they're both teh same product, just packaged differently) have noticed better throttle response, increased MPG, and smoother driving, but not necessarily more HP.
Stick wtih stock and throw the money toward cam gears, intake, or exhaust
Hate to say it but I disagree. Since installing my screamin deamon, wires, and autolite doubleplats, I've noticed way more torque on the high end. Before I installed this, I noticed some miss firing, and just a general lack of torque above 4000 rpms. Now the revving is much smoother, and the torque is there.
IMHO It's a worth while mod, especially if you only have 150 bucks or so to spend.