Technically, yes. The suspension will be less compliant with a stiffer sway bar installed. The key here is that a stiffer sway bar does not translate into a stiffer ride like a stiffer coil spring would certainly do.
So, if you were riding your Spyder off road with large dips and ridges on one side and the opposite on the other side like you might encounter with an ATV, etc., then yes, the lowered compliance would most likely be a negative as long suspension travel is very important in this kind of condition. Especially at speed.
But when you are talking the relatively short suspension travel needed in street riding. Even on a pot holed surface (unless we are talking 6" + deep pot holes) then the potential reduction in compliance is never actually experienced to any noticeable degree outside of turning or crosswinds. And in these cases, the reduction in compliance is exactly what you are looking for.
Simply put. When you're in heavy off road situations, reduced compliance from a stiff sway bar is a negative. However, on the street, a controlled, targeted reduction in compliance means better traction, better control, more stability and flatter turns. What you want always depends on the conditions you are subjecting the vehicle to.
Thanks BR! Since I don't plan on doing any off-roading (hopefully), it sounds like it'll be worthwhile.