I took a long drive today in my newly acquired RX8, about 500 miles there and back. BTW it cruises nicely at 120 with plenty room to stretch it's legs even more!
Anyway on the highway the steering felt like it was sort of sticking. I'd be cruising along and either start to change lanes or go around a cruve (all this was at around 80mph) and the steering wheel would feel like it was sticking for lack of a better description. I don't think it was due to ruts in the road or anything because it happened on new sections of pavement and old. Once I turned the wheel with a little more force it would unstick and be fine for a while. Perhaps sticking is too strong of a word but it took slightly more force to break from my current path and move the steering wheel. Any ideas?

That behavior could be on purpose.

The power steering in the RX-8 is electric, not hydraulic, so it's entirely possible they have a slight "wiggle range" built into the controller where the power steering will ignore inputs smaller than (X) to avoid having the steering make all kinds of corrections due to statistically insignificant movement of the steering wheel.

At least that's a thought...

Now that I think about it, that occurs to me as well. At all different speeds...

It's not that it's sticky, it's more like not assisting until it is moved a little more. Maybe it is on purpose to give a little bit of that road feedback.

It's the sneeze factor.

At higher speeds the steering will be slightly heavier just off center.

This is done so the car tracks better and small inputs don't send the car weaving.