Since I've had my Steeda RSB installed for almost a year now I thought I'd post again ... I have a Ti with the handling package.
1st, the car still has understeer with just the Steeda RSB installed. No worries of oversteer, just reduced understeer.
2nd, driving I90 through Idaho at 75 to 85mph around corners marked with 45mph caution signs felt significantly better than previously with the stock RSB. I'd hate to admit it, but it actually feels better than my 2011 Brembo Mustang does on the the same corners. I just drove the same route in the Mustang and it wasn't long before I started thinking about sway bars for it. Previously, the Mustang had felt way better than the Focus on that drive.
Can't say anything about whther or not actual grip in corners has improved, but confidence and "feel" definately has.
2012 Focus Ti Hatch, Blue Candy
2011 Mustang GT, Grabber Blue, 6spd
1978 Mustang II, 351W, Tremec 3550
1978 Mustang II, 2.3L Turbo, 5spd